[armpl-gcc] Make pkg-config files available (#34978)

* [armpl-gcc] Make pkg-config files available
  ARMpl pkgconfig files are located in a non-default location and do not have the
  .pc extension. Changing those both helps pkgconfig pick them up correctly, e.g.
  in the meson build of `py-scipy`.
* Address @annop-w comments
* symlink instead of cp.

Co-authored-by: Stephen Sachs <stesachs@amazon.com>

var/spack/repos/builtin/packages/armpl-gcc/package.py

@@ -17,7 +17,6 @@
     "amzn2": "RHEL-7",
 }
 
-
 _versions = {
     "22.1_gcc-11.2": {
         "RHEL-7": ("9ce7858525109cca8f4e1d533113b6410d55f10cc4db16c4742562da87a32f2b"),
@@ -262,3 +261,15 @@ def check_install(self):
         make("-C", armpl_example_dir, "ARMPL_DIR=" + armpl_dir)
         # clean up
         make("-C", armpl_example_dir, "ARMPL_DIR=" + armpl_dir, "clean")
+
+    @run_after("install")
+    def make_pkgconfig_files(self):
+        # ArmPL pkgconfig files do not have .pc extension and are thus not found by pkg-config
+        armpl_dir = get_armpl_prefix(self.spec)
+        for f in find(join_path(armpl_dir, "pkgconfig"), "*"):
+            symlink(f, f + ".pc")
+
+    def setup_dependent_build_environment(self, env, dependent_spec):
+        # pkgconfig directory is not in standard ("lib", "lib64", "share") location
+        armpl_dir = get_armpl_prefix(self.spec)
+        env.append_path("PKG_CONFIG_PATH", join_path(armpl_dir, "pkgconfig"))