Switch to pulling llvm from github.com directly until llvm mirror is fixed. (#189)

diff --git a/src/build.py b/src/build.py
index 0737dab..62390c4 100755
--- a/src/build.py
+++ b/src/build.py
@@ -103,7 +103,10 @@
 GITHUB_REMOTE = 'github'
 GITHUB_SSH = 'git@github.com:'
 GIT_MIRROR_BASE = 'https://chromium.googlesource.com/'
-LLVM_MIRROR_BASE = 'https://llvm.googlesource.com/'
+# TODO(sbc): We should be using llvm.googlesource.com but its currently
+# falling behind in its mirroring: b/37252800
+#LLVM_MIRROR_BASE = 'https://llvm.googlesource.com/'
+LLVM_MIRROR_BASE = 'https://github.com/llvm-mirror/'
 GITHUB_MIRROR_BASE = GIT_MIRROR_BASE + 'external/github.com/'
 WASM_GIT_BASE = GITHUB_MIRROR_BASE + 'WebAssembly/'
 EMSCRIPTEN_GIT_BASE = GITHUB_MIRROR_BASE + 'kripken/'