[runtimes] Improve the documentation for LIBCXX_ADDITIONAL_COMPILE_FLAGS (#112733)

This clarifies how that option is meant to be used to avoid confusion.
As a drive-by, also fix an incorrect usage in the recently-added GPU
caches.

GitOrigin-RevId: e67442486d5efd48235f62b438557bc95193fc48
1 file changed
tree: b0f86f3f24bc277bcdf2b063a870b850bc107fc6
  1. cmake/
  2. docs/
  3. include/
  4. src/
  5. test/
  6. .clang-format
  7. CMakeLists.txt
  8. LICENSE.TXT