Don't use dyndep scanner when preprocessing

Fixes #11504

mesonbuild/backend/ninjabackend.py

@@ -2954,6 +2954,8 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
     def add_dependency_scanner_entries_to_element(self, target, compiler, element, src):
         if not self.should_use_dyndeps_for_target(target):
             return
+        if isinstance(target, build.CompileTarget):
+            return
         extension = os.path.splitext(src.fname)[1][1:]
         if extension != 'C':
             extension = extension.lower()

test cases/fortran/22 preprocess/main.f90

@@ -0,0 +1,4 @@
+#define MYDEF program
+MYDEF foo
+    write (*,*) 'Hello, world!'
+end MYDEF foo

test cases/fortran/22 preprocess/meson.build

@@ -0,0 +1,7 @@
+project('preprocess', 'fortran')
+
+fc = meson.get_compiler('fortran')
+
+pp_files = fc.preprocess('main.f90', output: '@PLAINNAME@')
+
+library('foo', pp_files)