bootstub: Add "-znotext" flag.

LLD complains when linking bootstub because
of text relocations in trampoline.S file.
BFD also produces same error if "-ztext" is passed to the linker.

To match the currently expected behavior, pass "-znotext" to linker
flags.

BUG=chromium:1005468
BUG=chromium:1006338

TEST=No functional change yet.

Change-Id: If570b7c260d2bc3cd93e2656195c0509638a7650
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/bootstub/+/1816984
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Manoj Gupta <manojgupta@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
diff --git a/Makefile b/Makefile
index f582006..95a741e 100644
--- a/Makefile
+++ b/Makefile
@@ -41,7 +41,7 @@
 DEBUGFLAGS = -Wall
 CFLAGS     = $(OPTIMFLAGS) -fpic -fshort-wchar $(DEBUGFLAGS)
 CFLAGS     += -DEFI_FUNCTION_WRAPPER
-LDFLAGS    = -nostdlib -znocombreloc
+LDFLAGS    = -nostdlib -znocombreloc -znotext
 
 
 CRTOBJS       = $(EFICRT0)/crt0-efi-$(ARCH).o