[CI] Disable precompiled headers in pre-commit CI (#176563)

Spliced out from #176420 to make sure that CI is fine without PCH, which
are currently used by Flang.

.ci/monolithic-linux.sh

@@ -54,6 +54,7 @@ cmake -S "${MONOREPO_ROOT}"/llvm -B "${BUILD_DIR}" \
       -D CMAKE_CXX_FLAGS=-gmlt \
       -D CMAKE_C_COMPILER_LAUNCHER=sccache \
       -D CMAKE_CXX_COMPILER_LAUNCHER=sccache \
+      -D CMAKE_DISABLE_PRECOMPILE_HEADERS=ON \
       -D LIBCXX_CXX_ABI=libcxxabi \
       -D MLIR_ENABLE_BINDINGS_PYTHON=ON \
       -D LLDB_ENABLE_PYTHON=ON \

.ci/monolithic-windows.sh

@@ -43,6 +43,7 @@ cmake -S "${MONOREPO_ROOT}"/llvm -B "${BUILD_DIR}" \
       -D COMPILER_RT_BUILD_ORC=OFF \
       -D CMAKE_C_COMPILER_LAUNCHER=sccache \
       -D CMAKE_CXX_COMPILER_LAUNCHER=sccache \
+      -D CMAKE_DISABLE_PRECOMPILE_HEADERS=ON \
       -D MLIR_ENABLE_BINDINGS_PYTHON=ON \
       -D CMAKE_EXE_LINKER_FLAGS="/MANIFEST:NO" \
       -D CMAKE_MODULE_LINKER_FLAGS="/MANIFEST:NO" \