Improve handling of CFLAGS #356

Job	Run time
GCC 4.8 - CMake 0 - FIPS 0	6m 41s
GCC 4.8 - CMake 0 - FIPS 1	8m 40s
GCC 5 - CMake 0 - FIPS 0	8m 7s
GCC 5 - CMake 0 - FIPS 1	8m 28s
GCC 6 - CMake 0 - FIPS 0	6m 24s
GCC 7 - CMake 0 - FIPS 0	7m 2s
GCC 6 - CMake 0 - FIPS 1	8m 24s
GCC 7 - CMake 0 - FIPS 1	7m 50s
GCC 4.8 - CMake 1 - FIPS 0	6m 34s
GCC 8 - CMake 0 - FIPS 0	6m 34s
GCC 4.8 - CMake 1 - FIPS 1	7m 10s
C-std ubuntu-latest - 11 - Force CMake 0	2m 6s
GCC 5 - CMake 1 - FIPS 0	6m 33s
GCC 8 - CMake 0 - FIPS 1	7m 40s
GCC 5 - CMake 1 - FIPS 1	8m 3s
C-std ubuntu-latest - 11 - Force CMake 1	1m 35s
GCC 7 - CMake 1 - FIPS 0	6m 53s
GCC 6 - CMake 1 - FIPS 0	6m 38s
GCC 7 - CMake 1 - FIPS 1	8m 27s
GCC 6 - CMake 1 - FIPS 1	11m 47s
GCC 8 - CMake 1 - FIPS 0	7m 50s
GCC 8 - CMake 1 - FIPS 1	8m 46s
C-std ubuntu-latest - 99 - Force CMake 0	1m 46s
C-std ubuntu-latest - 99 - Force CMake 1	1m 34s
C-std macos-13 - 11 - Force CMake 0	1m 54s
C-std macos-13 - 11 - Force CMake 1	3m 16s
C-std macos-13 - 99 - Force CMake 0	2m 36s
C-std macos-13 - 99 - Force CMake 1	3m 48s
C-std macos-14-xlarge - 11 - Force CMake 0	1m 33s
C-std macos-14-xlarge - 11 - Force CMake 1	1m 31s
C-std macos-14-xlarge - 99 - Force CMake 0	1m 51s
C-std macos-14-xlarge - 99 - Force CMake 1	1m 34s
C-std windows-latest - 11 - Force CMake 0	4m 10s
C-std windows-latest - 11 - Force CMake 1	5m 5s
C-std windows-latest - 99 - Force CMake 0	4m 49s
C-std windows-latest - 99 - Force CMake 1	2m 55s
	3h 16m 34s

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