build_symbolizer: Set LLVM_DEFAULT_TARGET_TRIPLE in llvm builds

Pass on the default target triple of the host clang to the LLVM builds
within the `build_symbolizer.sh` script.

Differential Revision: https://reviews.llvm.org/D128731

compiler-rt/lib/sanitizer_common/symbolizer/scripts/build_symbolizer.sh

@@ -118,6 +118,7 @@ if [[ ! -d ${LIBCXX_BUILD} ]]; then
     -DLIBCXX_ENABLE_EXCEPTIONS=OFF \
     -DLIBCXX_ENABLE_RTTI=OFF \
     -DLIBCXX_ENABLE_SHARED=OFF \
+    -DLLVM_DEFAULT_TARGET_TRIPLE="${TARGET_TRIPLE}" \
   $LLVM_SRC
 fi
 cd ${LIBCXX_BUILD}
@@ -137,6 +138,7 @@ if [[ ! -d ${LLVM_BUILD} ]]; then
     -DCMAKE_C_FLAGS_RELEASE="${LLVM_FLAGS}" \
     -DCMAKE_CXX_FLAGS_RELEASE="${LLVM_FLAGS}" \
     -DLLVM_TABLEGEN=$TBLGEN \
+    -DLLVM_DEFAULT_TARGET_TRIPLE="${TARGET_TRIPLE}" \
     -DLLVM_ENABLE_ZLIB=ON \
     -DLLVM_ENABLE_TERMINFO=OFF \
     -DLLVM_ENABLE_THREADS=OFF \