$ make print-CFLAGS
CFLAGS=-fsanitize=address -Og -g

Trick from various sources:
https://stackoverflow.com/questions/16467718/how-to-print-out-a-variable-in-makefile
https://www.cmcrossroads.com/article/printing-value-makefile-variableSigned-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-Id: <20180104160523.22995-4-marcandre.lureau@redhat.com>
Tested-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>