Minimally support Flymake in Emacs C sources

The check-syntax target is enabled the use of Flymake's "legacy"
backend, flymake-proc-legacy-flymake in src/*.c.  It works quite well
with C sources.  The green light for this change had already been
given some time ago in

https://lists.gnu.org/archive/html/emacs-devel/2017-10/msg00385.html

* src/Makefile.in (check-syntax): New target.
(.PHONY): Add check-syntax.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/Makefile.in b/src/Makefile.in
index 1d23425969c..a1ec0bd7f7b 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -754,3 +754,8 @@ else
 endif
         @: Compile some files earlier to speed up further compilation.
         $(MAKE) -C ../lisp compile-first EMACS="$(bootstrap_exe)"
+
+### Flymake support (for C only)
+check-syntax:
+        $(AM_V_CC)$(CC) -c $(CPPFLAGS) $(ALL_CFLAGS) ${CHK_SOURCES} || true
+.PHONY: check-syntax