There's also 'AX_APPEND_COMPILE_FLAGS' [1] (and its dependency 'AX_CHECK_COMPILE_FLAG' [2]), next to many other (related or unrelated) macros in the autoconf archive.

[1] https://www.gnu.org/software/autoconf-archive/ax_append_comp...

[2] https://www.gnu.org/software/autoconf-archive/ax_check_compi...