[docs] Prefer --gcc-install-dir= to deprecated GCC_INSTALL_PREFIX (#85458)
Setting GCC_INSTALL_PREFIX leads to a warning (#77537).
Link:
https://discourse.llvm.org/t/add-gcc-install-dir-deprecate-gcc-toolchain-and-remove-gcc-install-prefix/65091
Link:
https://discourse.llvm.org/t/correct-cmake-parameters-for-building-clang-and-lld-for-riscv/72833
GitOrigin-RevId: 9936ac308332796bf16024ce30a4aa1fba2cce66
diff --git a/docs/SupportAndFAQ.rst b/docs/SupportAndFAQ.rst
index afc532c..9e6974d 100644
--- a/docs/SupportAndFAQ.rst
+++ b/docs/SupportAndFAQ.rst
@@ -279,11 +279,12 @@
Enabling the OpenMP runtime will perform a two-stage build for you.
If your host compiler is different from your system-wide compiler, you may need
-to set the CMake variable `GCC_INSTALL_PREFIX` so clang will be able to find the
-correct GCC toolchain in the second stage of the build.
+to set ``CMAKE_{C,CXX}_FLAGS`` like
+``--gcc-install-dir=/usr/lib/gcc/x86_64-linux-gnu/12`` so that clang will be
+able to find the correct GCC toolchain in the second stage of the build.
For example, if your system-wide GCC installation is too old to build LLVM and
-you would like to use a newer GCC, set the CMake variable `GCC_INSTALL_PREFIX`
+you would like to use a newer GCC, set ``--gcc-install-dir=``
to inform clang of the GCC installation you would like to use in the second stage.
Q: How can I include OpenMP offloading support in my CMake project?
