waf: cmake: define a dictionary of supported generators

On Windows, using MSYS Makefiles generator doesn't work very well when the
CMakeLists.txt files use custom commands with paths as arguments. Furthermore,
MinGW Makefiles generator can't be used if sh.exe is in the system's path and
some build systems rely on sh for certain tasks (which is the case of PX4
Firmware build). Because of that, the list of generators for Windows has been
narrowed to Ninja and NMake Makefiles.

Tools/ardupilotwaf/cmake.py

@@ -381,13 +381,28 @@ def _check_min_version(cfg):
             cfg.fatal('cmake must be at least at version %s' % minver_str)
         cfg.end_msg(m.group(0))
 
+generators = dict(
+    default=[
+        (['ninja', 'ninja-build'], 'Ninja'),
+        (['make'], 'Unix Makefiles'),
+    ],
+    win32=[
+        (['ninja', 'ninja-build'], 'Ninja'),
+        (['nmake'], 'NMake Makefiles'),
+    ],
+)
+
 def configure(cfg):
     cfg.find_program('cmake')
 
     if cfg.env.CMAKE_MIN_VERSION:
         _check_min_version(cfg)
 
-    cfg.find_program(['ninja', 'ninja-build'], var='NINJA', mandatory=False)
-    cfg.env.CMAKE_GENERATOR_OPTION = ''
-    if cfg.env.NINJA:
-        cfg.env.CMAKE_GENERATOR_OPTION = '-GNinja'
+    l = generators.get(Utils.unversioned_sys_platform(), generators['default'])
+    for names, generator in l:
+        if cfg.find_program(names, mandatory=False):
+            cfg.env.CMAKE_GENERATOR_OPTION = '-G%s' % generator
+            break
+    else:
+        cfg.fatal("cmake: couldn't find a suitable CMake generator. " +
+                  "The ones supported by this Waf tool for this platform are: %s" % ', '.join(g for _, g in l))