SquishTests: Retire Qt 5.4 on Linux

We never used it on Mac and on Linux it doesn't provide any value. On
Windows it's still the only kit using gcc, so it should not be removed
without a replacement.

Change-Id: I330f8d33a98759a762fd5cc97d5d55e03d1d03d6
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

tests/system/README

@@ -18,7 +18,6 @@ Qt version for the respective toolchain with the components (if available):
 The exact versions and toolchains are:
 
 Linux:
-Qt 5.4.1 (gcc)
 Qt 5.10.1 (gcc)
 Qt 5.14.1 (gcc)
 Qt 6.2.4 (gcc)

tests/system/shared/classes.py

@@ -25,7 +25,7 @@ class Targets:
     @staticmethod
     def availableTargetClasses(ignoreValidity=False):
         availableTargets = set(Targets.ALL_TARGETS)
-        if platform.system() == 'Darwin':
+        if platform.system() not in ('Windows', 'Microsoft'):
             availableTargets.remove(Targets.DESKTOP_5_4_1_GCC)
         return availableTargets
 
@@ -84,7 +84,7 @@ class QtPath:
     def getPaths(pathSpec):
         qtTargets = [Targets.DESKTOP_5_10_1_DEFAULT, Targets.DESKTOP_5_14_1_DEFAULT,
                      Targets.DESKTOP_6_2_4]
-        if platform.system() != 'Darwin':
+        if platform.system() in ('Windows', 'Microsoft'):
             qtTargets.append(Targets.DESKTOP_5_4_1_GCC)
         if pathSpec == QtPath.DOCS:
             return map(lambda target: QtPath.docsPath(target), qtTargets)

tests/system/shared/project.py

@@ -533,7 +533,7 @@ def __getSupportedPlatforms__(text, templateName, getAsStrings=False, ignoreVali
             result = result.union(set([Targets.DESKTOP_5_10_1_DEFAULT,
                                        Targets.DESKTOP_5_14_1_DEFAULT,
                                        Targets.DESKTOP_6_2_4]))
-            if platform.system() != 'Darwin':
+            if platform.system() in ('Windows', 'Microsoft'):
                 result.add(Targets.DESKTOP_5_4_1_GCC)
     elif 'Platform independent' in text:
         result = Targets.desktopTargetClasses()