Speculatively fix build bots

This adds CFLAGS as well as CXXFLAGS for disabling implicit function
declarations in both CMake and Makefiles. Hopefully addresses the
issues in:

https://lab.llvm.org/buildbot/#/builders/105/builds/24314
diff --git a/MultiSource/Applications/siod/CMakeLists.txt b/MultiSource/Applications/siod/CMakeLists.txt
index 6473e22..989c628 100644
--- a/MultiSource/Applications/siod/CMakeLists.txt
+++ b/MultiSource/Applications/siod/CMakeLists.txt
@@ -1,4 +1,6 @@
-list(APPEND CPPFLAGS -D__USE_MISC -D__USE_GNU -D__USE_SVID -D__USE_XOPEN_EXTENDED -D__USE_XOPEN -Dunix -Wno-implicit-function-declaration)
+list(APPEND CPPFLAGS -D__USE_MISC -D__USE_GNU -D__USE_SVID -D__USE_XOPEN_EXTENDED -D__USE_XOPEN -Dunix)
+list(APPEND CXXFLAGS -Wno-implicit-function-declaration)
+list(APPEND CFLAGS -Wno-implicit-function-declaration)
 list(APPEND LDFLAGS -lm)
 set(RUN_OPTIONS -v1 test.scm)
 llvm_multisource(siod)
diff --git a/MultiSource/Applications/siod/Makefile b/MultiSource/Applications/siod/Makefile
index 674927a..69d9aec 100644
--- a/MultiSource/Applications/siod/Makefile
+++ b/MultiSource/Applications/siod/Makefile
@@ -1,6 +1,8 @@
 LEVEL = ../../..
 PROG     = siod
 CPPFLAGS = -D__USE_MISC -D__USE_GNU -D__USE_SVID -D__USE_XOPEN_EXTENDED -D__USE_XOPEN -Dunix
+CXXFLAGS += -Wno-implicit-function-declaration
+CFLAGS += -Wno-implicit-function-declaration
 LDFLAGS  = -lm $(TOOLLINKOPTS)
 
 RUN_OPTIONS = -v1 $(PROJ_SRC_DIR)/test.scm
diff --git a/MultiSource/Benchmarks/MiBench/office-ispell/CMakeLists.txt b/MultiSource/Benchmarks/MiBench/office-ispell/CMakeLists.txt
index a102311..b887ed4 100644
--- a/MultiSource/Benchmarks/MiBench/office-ispell/CMakeLists.txt
+++ b/MultiSource/Benchmarks/MiBench/office-ispell/CMakeLists.txt
@@ -1,4 +1,6 @@
-list(APPEND CPPFLAGS  -Wno-implicit-function-declaration -Dconst=)
+list(APPEND CPPFLAGS -Dconst=)
+list(APPEND CXXFLAGS -Wno-implicit-function-declaration)
+list(APPEND CFLAGS -Wno-implicit-function-declaration)
 list(APPEND LDFLAGS -lm)
 set(RUN_OPTIONS -a -d americanmed+ < large.txt)
 llvm_multisource(office-ispell)
diff --git a/MultiSource/Benchmarks/MiBench/office-ispell/Makefile b/MultiSource/Benchmarks/MiBench/office-ispell/Makefile
index 5f3b840..fe58848 100644
--- a/MultiSource/Benchmarks/MiBench/office-ispell/Makefile
+++ b/MultiSource/Benchmarks/MiBench/office-ispell/Makefile
@@ -2,6 +2,8 @@
 
 PROG     = office-ispell
 CPPFLAGS = -Dconst=
+CXXFLAGS += -Wno-implicit-function-declaration
+CFLAGS += -Wno-implicit-function-declaration
 LDFLAGS  = -lm
 RUN_OPTIONS = -a -d $(PROJ_SRC_DIR)/americanmed+
 STDIN_FILENAME = $(PROJ_SRC_DIR)/large.txt
diff --git a/MultiSource/Benchmarks/Prolangs-C/archie-client/CMakeLists.txt b/MultiSource/Benchmarks/Prolangs-C/archie-client/CMakeLists.txt
index f939f2a..190a4c3 100644
--- a/MultiSource/Benchmarks/Prolangs-C/archie-client/CMakeLists.txt
+++ b/MultiSource/Benchmarks/Prolangs-C/archie-client/CMakeLists.txt
@@ -1,5 +1,6 @@
 include(CheckFunctionExists)
-list(APPEND CPPFLAGS -Wno-implicit-function-declaration)
+list(APPEND CFLAGS -Wno-implicit-function-declaration)
+list(APPEND CXXFLAGS -Wno-implicit-function-declaration)
 check_function_exists(re_comp HAVE_RE_COMP)
 
 if(HAVE_RE_COMP)
diff --git a/MultiSource/Benchmarks/Prolangs-C/archie-client/Makefile b/MultiSource/Benchmarks/Prolangs-C/archie-client/Makefile
index 700b6b1..ce0ac29 100644
--- a/MultiSource/Benchmarks/Prolangs-C/archie-client/Makefile
+++ b/MultiSource/Benchmarks/Prolangs-C/archie-client/Makefile
@@ -2,6 +2,9 @@
 
 include $(LEVEL)/Makefile.config
 
+CXXFLAGS += -Wno-implicit-function-declaration
+CFLAGS += -Wno-implicit-function-declaration
+
 # This test uses the deprecated re_comp functions.
 ifdef HAVE_RE_COMP
 PROG = archie
diff --git a/MultiSource/Benchmarks/Prolangs-C/bison/CMakeLists.txt b/MultiSource/Benchmarks/Prolangs-C/bison/CMakeLists.txt
index 1f820c9..6d43f2f 100644
--- a/MultiSource/Benchmarks/Prolangs-C/bison/CMakeLists.txt
+++ b/MultiSource/Benchmarks/Prolangs-C/bison/CMakeLists.txt
@@ -1,4 +1,5 @@
-list(APPEND CPPFLAGS -Wno-implicit-function-declaration)
+list(APPEND CFLAGS -Wno-implicit-function-declaration)
+list(APPEND CXXFLAGS -Wno-implicit-function-declaration)
 set(RUN_OPTIONS parse.y.in -v)
 llvm_multisource(mybison)
 llvm_test_data(mybison parse.y.in)
diff --git a/MultiSource/Benchmarks/Prolangs-C/bison/Makefile b/MultiSource/Benchmarks/Prolangs-C/bison/Makefile
index de1513b..b5f3b79 100644
--- a/MultiSource/Benchmarks/Prolangs-C/bison/Makefile
+++ b/MultiSource/Benchmarks/Prolangs-C/bison/Makefile
@@ -1,5 +1,8 @@
 LEVEL = ../../../..
 
+CFLAGS += -Wno-implicit-function-declaration
+CXXFLAGS += -Wno-implicit-function-declaration
+
 PROG = mybison
 RUN_OPTIONS = $(PROJ_SRC_DIR)/parse.y.in -v
 include $(LEVEL)/MultiSource/Makefile.multisrc
diff --git a/MultiSource/Benchmarks/Prolangs-C/plot2fig/CMakeLists.txt b/MultiSource/Benchmarks/Prolangs-C/plot2fig/CMakeLists.txt
index c701958..1d593a8 100644
--- a/MultiSource/Benchmarks/Prolangs-C/plot2fig/CMakeLists.txt
+++ b/MultiSource/Benchmarks/Prolangs-C/plot2fig/CMakeLists.txt
@@ -1,6 +1,7 @@
 include(CheckFunctionExists)
 check_function_exists(re_comp HAVE_RE_COMP)
-list(APPEND CPPFLAGS -Wno-implicit-function-declaration)
+list(APPEND CXXFLAGS -Wno-implicit-function-declaration)
+list(APPEND CFLAGS -Wno-implicit-function-declaration)
 if(HAVE_RE_COMP)
   list(APPEND LDFLAGS -lm)
   llvm_multisource(plot2fig)
diff --git a/MultiSource/Benchmarks/Prolangs-C/plot2fig/Makefile b/MultiSource/Benchmarks/Prolangs-C/plot2fig/Makefile
index 6be1189..086d45f 100644
--- a/MultiSource/Benchmarks/Prolangs-C/plot2fig/Makefile
+++ b/MultiSource/Benchmarks/Prolangs-C/plot2fig/Makefile
@@ -1,6 +1,9 @@
 LEVEL = ../../../..
 include $(LEVEL)/Makefile.config
 
+CFLAGS += -Wno-implicit-function-declaration
+CXXFLAGS += -Wno-implicit-function-declaration
+
 # This test uses the deprecated re_comp functions.
 ifdef HAVE_RE_COMP
 PROG = plot2fig
diff --git a/SingleSource/Regression/C/gcc-c-torture/execute/ieee/CMakeLists.txt b/SingleSource/Regression/C/gcc-c-torture/execute/ieee/CMakeLists.txt
index bdbd7b8..76718e9 100644
--- a/SingleSource/Regression/C/gcc-c-torture/execute/ieee/CMakeLists.txt
+++ b/SingleSource/Regression/C/gcc-c-torture/execute/ieee/CMakeLists.txt
@@ -1,5 +1,6 @@
 # GCC C Torture Suite is conventionally run without warnings
 list(APPEND CFLAGS -Wno-implicit-function-declaration -w)
+list(APPEND CXXFLAGS -Wno-implicit-function-declaration -w)
 set(TestsToSkip)
 
 ##