meson: Add sha1 library options

v2: Set the define for xha1.c programatically, rather than using loads
of conditionals.
4 jobs for meson-sha1-options in 6 minutes and 25 seconds (queued for 4 seconds)
Status Name Job ID Coverage
  Docker Image
passed debian-testing #846896

00:00:33

 
  Build And Test
passed autotools-build-and-test #846897

00:05:51

passed meson-build-and-test #846898

00:01:53

 
  External
passed continuous-integration/appveyor/branch