Install emacs-module.h (Bug#31929)

* Makefile.in (includedir): New variable.
(install-arch-indep): Install emacs-module.h.
(uninstall): Uninstall emacs-module.h.

Makefile.in

@@ -151,6 +151,9 @@ libexecdir=@libexecdir@
 # Currently only used for the systemd service file.
 libdir=@libdir@
 
+# Where to install emacs-module.h.
+includedir=@includedir@
+
 # Where to install Emacs's man pages.
 # Note they contain cross-references that expect them to be in section 1.
 mandir=@mandir@
@@ -560,6 +563,8 @@ set_installuser=for installuser in $${LOGNAME} $${USERNAME} $${USER} \
 ## See also these comments from 2004 about cp -r working fine:
 ## https://lists.gnu.org/r/autoconf-patches/2004-11/msg00005.html
 install-arch-indep: lisp install-info install-man ${INSTALL_ARCH_INDEP_EXTRA}
+	umask 022 && $(MKDIR_P) -m 0755 $(includedir)
+	$(INSTALL_DATA) src/emacs-module.h $(includedir)/emacs-module.h
 	-set ${COPYDESTS} ; \
 	unset CDPATH; \
 	$(set_installuser); \
@@ -743,6 +748,7 @@ install-strip:
 ###
 ### Don't delete the lisp and etc directories if they're in the source tree.
 uninstall: uninstall-$(NTDIR) uninstall-doc
+	rm -f $(includedir)/emacs-module.h
 	$(MAKE) -C lib-src uninstall
 	-unset CDPATH; \
 	for dir in "$(DESTDIR)${lispdir}" "$(DESTDIR)${etcdir}" ; do 	\