diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -466,11 +466,15 @@
     ${NINJA} -vC "${BUILD_DIR}/libcxxabi" check-cxxabi
 ;;
 aarch64)
+    export CC=/usr/local/bin/cc
+    export CXX=/usr/local/bin/c++
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/AArch64.cmake"
     check-cxx-cxxabi
 ;;
 aarch64-noexceptions)
+    export CC=/usr/local/bin/cc
+    export CXX=/usr/local/bin/c++
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/AArch64.cmake" \
     -DLIBCXX_ENABLE_EXCEPTIONS=OFF \
@@ -479,22 +483,30 @@
 ;;
 # Aka Armv8 32 bit
 armv8)
+    export CC=/usr/local/bin/cc
+    export CXX=/usr/local/bin/c++
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv8Arm.cmake"
     check-cxx-cxxabi
 ;;
 armv8-noexceptions)
+    export CC=/usr/local/bin/cc
+    export CXX=/usr/local/bin/c++
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv8Thumb-noexceptions.cmake"
     check-cxx-cxxabi
 ;;
 # Armv7 32 bit. One building Arm only one Thumb only code.
 armv7)
+    export CC=/usr/local/bin/cc
+    export CXX=/usr/local/bin/c++
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7Arm.cmake"
     check-cxx-cxxabi
 ;;
 armv7-noexceptions)
+    export CC=/usr/local/bin/cc
+    export CXX=/usr/local/bin/c++
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7Thumb-noexceptions.cmake"
     check-cxx-cxxabi