build: split ARM crc & crypto extension checks

We currently perform the same check twice, to put the same set of flags
in two different variables. Split the checks so we test for crc and crypto
extensions independently.

If we don't want to split, we should just delete the second AX_CHECK_COMPILE_FLAG
check, and set ARM_CRC_CXXFLAGS & ARM_CRC_CXXFLAGS at the same time.

configure.ac

@@ -588,8 +588,8 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
 CXXFLAGS="$TEMP_CXXFLAGS"
 
 # ARM
-AX_CHECK_COMPILE_FLAG([-march=armv8-a+crc+crypto], [ARM_CRC_CXXFLAGS="-march=armv8-a+crc+crypto"], [], [$CXXFLAG_WERROR])
-AX_CHECK_COMPILE_FLAG([-march=armv8-a+crc+crypto], [ARM_SHANI_CXXFLAGS="-march=armv8-a+crc+crypto"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-march=armv8-a+crc], [ARM_CRC_CXXFLAGS="-march=armv8-a+crc"], [], [$CXXFLAG_WERROR])
+AX_CHECK_COMPILE_FLAG([-march=armv8-a+crypto], [ARM_SHANI_CXXFLAGS="-march=armv8-a+crypto"], [], [$CXXFLAG_WERROR])
 
 TEMP_CXXFLAGS="$CXXFLAGS"
 CXXFLAGS="$ARM_CRC_CXXFLAGS $CXXFLAGS"