tests: Move build-by-default unit test to common tests

Also add a test() that can be run on all platforms.

Currently unit tests are only run on Linux, so this was only testing the
Ninja backend. This change reveals that build-by-default was broken with
the Visual Studio backend.

run_unittests.py

@@ -566,7 +566,7 @@ class LinuxlikeTests(unittest.TestCase):
         self._test_stds_impl(testdir, cpp, 'cpp')
 
     def test_build_by_default(self):
-        testdir = os.path.join(self.unit_test_dir, '5 build by default')
+        testdir = os.path.join(self.common_test_dir, '137 build by default')
         self.init(testdir)
         self.build()
         genfile = os.path.join(self.builddir, 'generated.dat')

test cases/common/137 build by default/meson.build

@@ -0,0 +1,24 @@
+project('build on all', 'c')
+
+py3_mod = import('python3')
+py3 = py3_mod.find_python()
+
+executable('fooprog', 'foo.c', build_by_default : false)
+comp = files('mygen.py')
+mytarget = custom_target('gendat',
+  output : 'generated.dat',
+  input : 'source.txt',
+  command : [py3] + comp + ['@INPUT@', '@OUTPUT@'],
+  build_by_default : true,
+)
+
+ct_output = join_paths(meson.build_root(), 'generated.dat')
+exe_output = join_paths(meson.build_root(), 'fooprog')
+if host_machine.system() == 'windows'
+  exe_output += '.exe'
+endif
+
+ct_exists_exe_nexists = 'import os.path, sys; sys.exit(not os.path.exists(sys.argv[1]) and os.path.exists(sys.argv[2]))'
+
+test('check-build-by-default', py3,
+     args : ['-c', ct_exists_exe_nexists, ct_output, exe_output])

test cases/unit/5 build by default/meson.build

@@ -1,13 +0,0 @@
-project('build on all', 'c')
-
-py3_mod = import('python3')
-py3 = py3_mod.find_python()
-
-executable('fooprog', 'foo.c', build_by_default : false)
-comp = files('mygen.py')
-mytarget = custom_target('gendat',
-  output : 'generated.dat',
-  input : 'source.txt',
-  command : [py3] + comp + ['@INPUT@', '@OUTPUT@'],
-  build_by_default : true,
-)