Unity build reverts to normal for fortran fix

The `determine_ext_objs` function did not take into account that fortran
(and d) does not support unity builds. This caused failures in some
cases.

mesonbuild/backend/backends.py

@@ -45,6 +45,11 @@ if T.TYPE_CHECKING:
     InstallType = T.List[T.Tuple[str, str, T.Optional['FileMode']]]
     InstallSubdirsType = T.List[T.Tuple[str, str, T.Optional['FileMode'], T.Tuple[T.Set[str], T.Set[str]]]]
 
+# Languages that can mix with C or C++ but don't support unity builds yet
+# because the syntax we use for unity builds is specific to C/++/ObjC/++.
+# Assembly files cannot be unitified and neither can LLVM IR files
+LANGS_CANT_UNITY = ('d', 'fortran')
+
 class TestProtocol(enum.Enum):
 
     EXITCODE = 0
@@ -637,6 +642,9 @@ class Backend:
             unity_size = self.get_option_for_target(OptionKey('unity_size'), extobj.target)
 
             for comp, srcs in compsrcs.items():
+                if comp.language in LANGS_CANT_UNITY:
+                    sources += srcs
+                    continue
                 for i in range(len(srcs) // unity_size + 1):
                     osrc = self.get_unity_source_file(extobj.target,
                                                       comp.get_default_suffix(), i)

mesonbuild/backend/ninjabackend.py

@@ -626,11 +626,6 @@ int dummy;
             srcs[f] = s
         return srcs
 
-    # Languages that can mix with C or C++ but don't support unity builds yet
-    # because the syntax we use for unity builds is specific to C/++/ObjC/++.
-    # Assembly files cannot be unitified and neither can LLVM IR files
-    langs_cant_unity = ('d', 'fortran')
-
     def get_target_source_can_unity(self, target, source):
         if isinstance(source, File):
             source = source.fname
@@ -638,7 +633,7 @@ int dummy;
            self.environment.is_assembly(source):
             return False
         suffix = os.path.splitext(source)[1][1:].lower()
-        for lang in self.langs_cant_unity:
+        for lang in backends.LANGS_CANT_UNITY:
             if lang not in target.compilers:
                 continue
             if suffix in target.compilers[lang].file_suffixes:
@@ -769,7 +764,7 @@ int dummy;
         if is_unity:
             # Warn about incompatible sources if a unity build is enabled
             langs = set(target.compilers.keys())
-            langs_cant = langs.intersection(self.langs_cant_unity)
+            langs_cant = langs.intersection(backends.LANGS_CANT_UNITY)
             if langs_cant:
                 langs_are = langs = ', '.join(langs_cant).upper()
                 langs_are += ' are' if len(langs_cant) > 1 else ' is'