Include api dir in distribution

Also, don't create empty Doxygen tag and api directory

.github/workflows/action.yml

@@ -142,7 +142,7 @@ jobs:
         if: startsWith(matrix.os,'ubuntu')
         run: |
           sudo apt-get update
-          sudo apt-get install -y libtool-bin libogg-dev doxygen libxml2-utils w3c-sgml-lib
+          sudo apt-get install -y libtool-bin libogg-dev
 
       - name: Install Windows dependencies
         if: startsWith(matrix.os,'windows')

configure.ac

@@ -375,6 +375,12 @@ if test "x$enable_doxygen_docs" != xfalse ; then
 fi
 AM_CONDITIONAL(FLaC__HAS_DOXYGEN, test -n "$DOXYGEN")
 
+if test  "x$DOXYGEN" = "x"; then
+	AC_CHECK_FILE($srcdir/doc/FLAC.tag,[HAVE_PREBUILT_FLAC_TAG=yes])
+	AC_CHECK_FILE($srcdir/doc/api/modules.html,[HAVE_PREBUILT_API_DIR=yes])
+fi
+AM_CONDITIONAL(FLaC__HAS_PREBUILT_DOXYGEN, test "x$HAVE_PREBUILD_FLAG_TAG$HAVEPREBUILD_API_DIR" = "xyesyes")
+
 AC_ARG_ENABLE(local-xmms-plugin,
 AS_HELP_STRING([--enable-local-xmms-plugin],[Install XMMS plugin to ~/.xmms/Plugins instead of system location]),
 [case "${enableval}" in

doc/Makefile.am

@@ -25,17 +25,38 @@ FLAC.tag: Doxyfile
 	rm -rf api
 	mv doxytmp/html api
 	rm -rf doxytmp
-else
-FLAC.tag:
-	touch $@
-	mkdir -p api
-endif
 
 doc_DATA = \
 	FLAC.tag
+else
+if FLaC__HAS_PREBUILT_DOXYGEN
+doc_DATA = \
+	FLAC.tag
+endif
+endif
 
 EXTRA_DIST = Doxyfile.in doxygen.footer.html \
-	isoflac.txt $(doc_DATA) CMakeLists.txt
+	isoflac.txt $(doc_DATA) CMakeLists.txt \
+	api
 
+if FLaC__HAS_DOXYGEN
+# The install targets don't copy whole directories so we have to
+# handle 'api/' specially:
+install-data-local:
+	$(mkinstalldirs) $(DESTDIR)$(docdir)/api
+	(cd $(builddir)/api && $(INSTALL_DATA) * $(DESTDIR)$(docdir)/api)
+uninstall-local:
+	rm -rf $(DESTDIR)$(docdir)/api
 distclean-local:
 	rm -rf FLAC.tag api doxytmp
+endif
+
+if FLaC__HAS_PREBUILT_DOXYGEN
+# The install targets don't copy whole directories so we have to
+# handle 'api/' specially:
+install-data-local:
+	$(mkinstalldirs) $(DESTDIR)$(docdir)/api
+	(cd $(builddir)/api && $(INSTALL_DATA) * $(DESTDIR)$(docdir)/api)
+uninstall-local:
+	rm -rf $(DESTDIR)$(docdir)/api
+endif