Patch /usr/bin/file to file when on nixos (#30718)

These changes make many packages build on nixos where nearly nothing
comes from /bin or /usr/bin (the only things in "system locations" are
/bin/sh and /usr/bin/env, all the rest is found through PATH).

Many configuration scripts hardcode /usr/bin/file instead of using the
one from PATH. This patches them to use file from PATH.

lib/spack/spack/build_systems/autotools.py

@@ -238,6 +238,15 @@ def runs_ok(script_abs_path):
             fs.copy(substitutes[name], abs_path)
             os.chmod(abs_path, mode)
 
+    @run_before("configure")
+    def _patch_usr_bin_file(self):
+        """On NixOS file is not available in /usr/bin/file. Patch configure
+        scripts to use file from path."""
+
+        if self.spec.os.startswith("nixos"):
+            for configure_file in fs.find(".", files=["configure"], recursive=True):
+                fs.filter_file("/usr/bin/file", "file", configure_file, string=True)
+
     @run_before("configure")
     def _set_autotools_environment_variables(self):
         """Many autotools builds use a version of mknod.m4 that fails when