TST: use platform specific anchors in RPATH entries

macOS requires using `@loader_path` in place of `$ORIGIN`.

Author: dnicolodi

tests/packages/sharedlib-in-package/meson.build

@@ -6,5 +6,7 @@ project('sharedlib-in-package', 'c', version: '1.0.0')
 
 py = import('python').find_installation(pure: false)
 
+origin = build_machine.system() == 'darwin' ? '@loader_path' : '$ORIGIN'
+
 subdir('src')
 subdir('mypkg')

tests/packages/sharedlib-in-package/mypkg/meson.build

@@ -11,8 +11,8 @@ py.extension_module(
     # install_rpath is not exposed in the Meson introspection data in Meson
     # versions prior to 1.6.0 and thus cannot be set by meson-python when
     # building the Python wheel. Use link_args to set the RPATH.
-    # install_rpath: '$ORIGIN',
-    link_args: '-Wl,-rpath,$ORIGIN',
+    # install_rpath: f'@origin@',
+    link_args: f'-Wl,-rpath,@origin@',
 )
 
 py.install_sources(

tests/packages/sharedlib-in-package/src/meson.build

@@ -33,8 +33,8 @@ lib = shared_library(
     # install_rpath is not exposed in the Meson introspection data in Meson
     # versions prior to 1.6.0 and thus cannot be set by meson-python when
     # building the Python wheel. Use link_args to set the RPATH.
-    # install_rpath: '$ORIGIN/sub',
-    link_args: '-Wl,-rpath,$ORIGIN/sub',
+    # install_rpath: f'@origin@/sub',
+    link_args: f'-Wl,-rpath,@origin@/sub',
 )
 
 lib_dep = declare_dependency(