Enable searching system crossfile locations on more platforms

There's no reason not to also look in these places on Cygwin or OSX.  Don't
do this on Windows, as these paths aren't meaningful there.

Move test_cross_file_system_paths from LinuxlikeTests to AllPlatformTests.

mesonbuild/coredata.py

@@ -222,17 +222,17 @@ class CoreData:
         (after resolving variables and ~), return that absolute path. Next,
         check if the file is relative to the current source dir. If the path
         still isn't resolved do the following:
-            Linux + BSD:
+            Windows:
+                - Error
+            *:
                 - $XDG_DATA_HOME/meson/cross (or ~/.local/share/meson/cross if
                   undefined)
                 - $XDG_DATA_DIRS/meson/cross (or
                   /usr/local/share/meson/cross:/usr/share/meson/cross if undefined)
                 - Error
-            *:
-                - Error
-        BSD follows the Linux path and will honor XDG_* if set. This simplifies
-        the implementation somewhat, especially since most BSD users wont set
-        those environment variables.
+
+        Non-Windows follows the Linux path and will honor XDG_* if set. This
+        simplifies the implementation somewhat.
         """
         if filename is None:
             return None
@@ -242,7 +242,7 @@ class CoreData:
         path_to_try = os.path.abspath(filename)
         if os.path.exists(path_to_try):
             return path_to_try
-        if sys.platform == 'linux' or 'bsd' in sys.platform.lower():
+        if sys.platform != 'win32':
             paths = [
                 os.environ.get('XDG_DATA_HOME', os.path.expanduser('~/.local/share')),
             ] + os.environ.get('XDG_DATA_DIRS', '/usr/local/share:/usr/share').split(':')

run_unittests.py

@@ -1749,6 +1749,53 @@ int main(int argc, char **argv) {
                     self._run(ninja,
                               workdir=os.path.join(tmpdir, 'builddir'))
 
+    def test_cross_file_system_paths(self):
+        if is_windows():
+            raise unittest.SkipTest('system crossfile paths not defined for Windows (yet)')
+
+        testdir = os.path.join(self.common_test_dir, '1 trivial')
+        cross_content = textwrap.dedent("""\
+            [binaries]
+            c = '/usr/bin/cc'
+            ar = '/usr/bin/ar'
+            strip = '/usr/bin/ar'
+
+            [properties]
+
+            [host_machine]
+            system = 'linux'
+            cpu_family = 'x86'
+            cpu = 'i686'
+            endian = 'little'
+            """)
+
+        with tempfile.TemporaryDirectory() as d:
+            dir_ = os.path.join(d, 'meson', 'cross')
+            os.makedirs(dir_)
+            with tempfile.NamedTemporaryFile('w', dir=dir_, delete=False) as f:
+                f.write(cross_content)
+            name = os.path.basename(f.name)
+
+            with mock.patch.dict(os.environ, {'XDG_DATA_HOME': d}):
+                self.init(testdir, ['--cross-file=' + name], inprocess=True)
+                self.wipe()
+
+            with mock.patch.dict(os.environ, {'XDG_DATA_DIRS': d}):
+                os.environ.pop('XDG_DATA_HOME', None)
+                self.init(testdir, ['--cross-file=' + name], inprocess=True)
+                self.wipe()
+
+        with tempfile.TemporaryDirectory() as d:
+            dir_ = os.path.join(d, '.local', 'share', 'meson', 'cross')
+            os.makedirs(dir_)
+            with tempfile.NamedTemporaryFile('w', dir=dir_, delete=False) as f:
+                f.write(cross_content)
+            name = os.path.basename(f.name)
+
+            with mock.patch('mesonbuild.coredata.os.path.expanduser', lambda x: x.replace('~', d)):
+                self.init(testdir, ['--cross-file=' + name], inprocess=True)
+                self.wipe()
+
 
 class FailureTests(BasePlatformTests):
     '''
@@ -2546,50 +2593,6 @@ endian = 'little'
         self.init(testdir, ['-Db_lto=true'], default_args=False)
         self.build('reconfigure')
 
-    def test_cross_file_system_paths(self):
-        testdir = os.path.join(self.common_test_dir, '1 trivial')
-        cross_content = textwrap.dedent("""\
-            [binaries]
-            c = '/usr/bin/cc'
-            ar = '/usr/bin/ar'
-            strip = '/usr/bin/ar'
-
-            [properties]
-
-            [host_machine]
-            system = 'linux'
-            cpu_family = 'x86'
-            cpu = 'i686'
-            endian = 'little'
-            """)
-
-        with tempfile.TemporaryDirectory() as d:
-            dir_ = os.path.join(d, 'meson', 'cross')
-            os.makedirs(dir_)
-            with tempfile.NamedTemporaryFile('w', dir=dir_, delete=False) as f:
-                f.write(cross_content)
-            name = os.path.basename(f.name)
-
-            with mock.patch.dict(os.environ, {'XDG_DATA_HOME': d}):
-                self.init(testdir, ['--cross-file=' + name], inprocess=True)
-                self.wipe()
-
-            with mock.patch.dict(os.environ, {'XDG_DATA_DIRS': d}):
-                os.environ.pop('XDG_DATA_HOME', None)
-                self.init(testdir, ['--cross-file=' + name], inprocess=True)
-                self.wipe()
-
-        with tempfile.TemporaryDirectory() as d:
-            dir_ = os.path.join(d, '.local', 'share', 'meson', 'cross')
-            os.makedirs(dir_)
-            with tempfile.NamedTemporaryFile('w', dir=dir_, delete=False) as f:
-                f.write(cross_content)
-            name = os.path.basename(f.name)
-
-            with mock.patch('mesonbuild.coredata.os.path.expanduser', lambda x: x.replace('~', d)):
-                self.init(testdir, ['--cross-file=' + name], inprocess=True)
-                self.wipe()
-
     def test_vala_generated_source_buildir_inside_source_tree(self):
         '''
         Test that valac outputs generated C files in the expected location when