run_project_tests.py: Allow qt tests to skip on !macOS

We don't always have qmake installed (and it's good to test failure
paths too!) so we can't expect this to succeed in all cases. With the
following commit we'll use a test.json to test both pkg-config and
qmake, so we need to be able to skip.

run_project_tests.py

@@ -865,11 +865,6 @@ def skippable(suite, test):
     if test.endswith('34 gir static lib'):
         return True
 
-    # No frameworks test should be skipped on linux CI, as we expect all
-    # prerequisites to be installed
-    if mesonlib.is_linux():
-        return False
-
     # Boost test should only be skipped for windows CI build matrix entries
     # which don't define BOOST_ROOT
     if test.endswith('1 boost'):
@@ -877,14 +872,22 @@ def skippable(suite, test):
             return 'BOOST_ROOT' not in os.environ
         return False
 
-    # Qt is provided on macOS by Homebrew
-    if test.endswith('4 qt') and mesonlib.is_osx():
-        return False
+    # Not all OSes have all of the methods for qt (qmake and pkg-config), don't
+    # fail if that happens.
+    #
+    # On macOS we should have all of the requirements at all times.
+    if test.endswith('4 qt'):
+        return not mesonlib.is_osx()
 
     # Bindgen isn't available in all distros
     if test.endswith('12 bindgen'):
         return False
 
+    # No frameworks test should be skipped on linux CI, as we expect all
+    # prerequisites to be installed
+    if mesonlib.is_linux():
+        return False
+
     # Other framework tests are allowed to be skipped on other platforms
     return True