Bug 1451104 - part 1 - ensure compatible binutils for GCC; r=glandium

GCC will pick up whatever `as` is first in PATH when trying to assemble
files.  It expects this `as` to have at least as many features as the
`as` detected at configure time when GCC was originally built.  We
should ensure that GCC is always picking up an appropriate `as` by
adding its base directory to the search path; otherwise, we get peculiar
assembler errors.

build/build-clang/build-clang.py

@@ -517,6 +517,18 @@ if __name__ == "__main__":
         extra_asmflags = []
         extra_ldflags = []
 
+        # We want to ensure that the GCC we use for stage 1 always picks up the
+        # binutils it is packaged with, rather than the system binutils, which
+        # might be a much different version and therefore lacking in support for
+        # features GCC expects.
+        binutils_flags = ['-B', os.path.dirname(cc)]
+        if cc.endswith('gcc'):
+            extra_cflags += binutils_flags
+        if cxx.endswith('g++'):
+            extra_cxxflags += binutils_flags
+        if asm.endswith('gcc'):
+            extra_asmflags += binutils_flags
+
         if 'LD_LIBRARY_PATH' in os.environ:
             os.environ['LD_LIBRARY_PATH'] = ('%s/lib64/:%s' %
                                              (gcc_dir, os.environ['LD_LIBRARY_PATH']))

taskcluster/scripts/misc/build-llvm-dsymutil.sh

@@ -56,6 +56,9 @@ cmake \
   -DCMAKE_BUILD_TYPE=Release \
   -DLLVM_TARGETS_TO_BUILD=X86 \
   -DCMAKE_C_COMPILER=$HOME_DIR/src/gcc/bin/gcc \
+  -DCMAKE_CXX_COMPILER=$HOME_DIR/src/gcc/bin/g++ \
+  -DCMAKE_C_FLAGS="-B $HOME_DIR/src/gcc/bin" \
+  -DCMAKE_CXX_FLAGS="-B $HOME_DIR/src/gcc/bin" \
   ..
 
 export LD_LIBRARY_PATH=$HOME_DIR/src/gcc/lib64