Fix ARMv6 detection when CFLAGS modify target CPU architecture
* configure.ac (gcry_cv_cc_arm_arch_is_v6): Use compiler test instead of preprocessor test.
Old test was using C preprocessor to check ARM version macros and missed fact
that using different CFLAGS affect those macros (CFLAGS are not passed to
preprocessor checks).
(cherry picked from commit 6be3032048ee2466511d2384fcf2d28b856219b2)
- Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>