cmake: Allow overriding/take into account user flags

[hebasto]

bitcoin/cmake/introspection.cmake

Lines 230 to 231 in d3a10e6

	# Check for ARMv8 SHA-NI intrinsics.
	set(ARM_SHANI_CXXFLAGS -march=armv8-a+crypto)

Looks like these don't allow overriding/take into account user flags? i.e If I configure with -DCMAKE_CXX_FLAGS_RELEASE="-march=armv8-a+nocrypto", I'd expect the ARM SHA-NI check to fail, but it doesn't. Also doesn't seem to work with APPEND_CXXFLAGS, which should always be (globally) taken into account?

Originally posted in bitcoin#30454 (comment).

[fanquake]

What is the status of this? Otherwise we are reintroducing issues like bitcoin#28864, and generally, just shouldn't be ignoring user provided flags.

[hebasto]

What is the status of this? Otherwise we are reintroducing issues like bitcoin#28864, and generally, just shouldn't be ignoring user provided flags.

See #282.