nix: add support to build with GCC

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

src/meson.build

@@ -5,13 +5,22 @@ lib_sources = files(
 
 subdir('cpu')
 
-fmt = dependency('fmt', version : '>=10.1.0')
+
+lib_cpp_args = [ ]
+
+fmt = dependency('fmt', version : '>=10.1.0', static: true)
+if not fmt.found()
+  fmt = dependency('fmt', version : '>=10.1.0', static: false)
+  lib_cpp_args += 'DFMT_HEADER_ONLY'
+endif
+
 lib = library(
   meson.project_name(),
   lib_sources,
   dependencies: [fmt],
   include_directories: inc,
   install: true,
+  cpp_args: lib_cpp_args
 )
 
 import('pkgconfig').generate(lib)