56f68bcf1b
`if (.. EQUAL ..)` is used to compare numbers so if the LHS is not
a number the condition is evaluated as false, this prevents us from
setting the -march when building for aarch64 targets. and because
crc32 implementation in utils/ always use the crypto extension
intrinsics, this also breaks the build like
```
In file included from /home/fedora/scylla/utils/gz/crc_combine.cc:40:
/home/fedora/scylla/utils/clmul.hh:60:12: error: always_inline function 'vmull_p64' requires target feature 'aes', but would be inlined into functi
on 'clmul_u32' that is compiled without support for 'aes'
return vmull_p64(p1, p2);
^
```
so, in this change,
* compare two strings using `STREQUAL`.
* document the reason why we need to set the -march to the
specfied argument.
see also http://gcc.gnu.org/onlinedocs/gcc/AArch64-Options.html#g_t-march-and--mcpu-Feature-Modifiers
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes scylladb/scylladb#15553