Put internal include dirs at the beginning so they override ones coming from the system. Closes #372.

mesonbuild/backend/ninjabackend.py

@@ -1435,6 +1435,23 @@ rule FORTRAN_DEP_HACK
         if curdir ==  '':
             curdir = '.'
         commands += compiler.get_include_args(curdir, False)
+        # -I args work differently than other ones. In them the
+        # first found directory is used whereas for other flags
+        # (such as -ffoo -fno-foo) the latest one is used.
+        # Therefore put the internal include directories here
+        # at the beginning so they override args coming from
+        # e.g. pkg-config.
+        for i in target.get_include_dirs():
+            basedir = i.get_curdir()
+            for d in i.get_incdirs():
+                expdir =  os.path.join(basedir, d)
+                srctreedir = os.path.join(self.build_to_src, expdir)
+                bargs = compiler.get_include_args(expdir, i.is_system)
+                sargs = compiler.get_include_args(srctreedir, i.is_system)
+                commands += bargs
+                commands += sargs
+            for d in i.get_extra_build_dirs():
+                commands += compiler.get_include_args(d, i.is_system)
         for d in target.external_deps:
             if d.need_threads():
                 commands += compiler.thread_flags()
@@ -1476,17 +1493,6 @@ rule FORTRAN_DEP_HACK
             i = os.path.join(self.get_target_private_dir(target), compiler.get_pch_name(pchlist[0]))
             arr.append(i)
             pch_dep = arr
-        for i in target.get_include_dirs():
-            basedir = i.get_curdir()
-            for d in i.get_incdirs():
-                expdir =  os.path.join(basedir, d)
-                srctreedir = os.path.join(self.build_to_src, expdir)
-                bargs = compiler.get_include_args(expdir, i.is_system)
-                sargs = compiler.get_include_args(srctreedir, i.is_system)
-                commands += bargs
-                commands += sargs
-            for d in i.get_extra_build_dirs():
-                commands += compiler.get_include_args(d, i.is_system)
         custom_target_include_dirs = []
         for i in target.generated:
             if isinstance(i, build.CustomTarget):