test: add unit tests for x_sha1_* functions in os/xsha1.

Simple confirmation of known values, not exhaustive testing.

Tested with SHA-1 implementations from:
 - libcrypto (OpenSSL 3)
 - libgcrypt
 - libnettle
 - Solaris libmd

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2066>

test/meson.build

@@ -179,6 +179,7 @@ if build_xorg
      'input.c',
      'list.c',
      'misc.c',
+     'sha1.c',
      'signal-logging.c',
      'string.c',
      'test_xkb.c',