fix distclean with --disable-llvm.

automake requires distclean, distdir, and maintainer-clean rules to exist
even in conditional subdirs that are excluded from the build.
So create a dummy Makefile that has these 3 rules for the --disable-llvm case.
distdir will of course always fail in --disable-llvm.

libclamav/Makefile.am

@@ -18,7 +18,7 @@
 
 AM_CPPFLAGS = -I$(top_srcdir) -I@srcdir@/nsis $(LTDLINCL)
 lib_LTLIBRARIES =
-EXTRA_DIST =
+EXTRA_DIST = c++/Makefile.nollvm.in
 if ENABLE_UNRAR
 
 AM_CPPFLAGS += -DWARN_DLOPEN_FAIL
@@ -118,6 +118,9 @@ SUBDIRS=c++
 else
 LLVMLIBADD=libclamav_nocxx.la
 LLVMDEP=libclamav_nocxx.la
+c++/Makefile: c++/Makefile.nollvm.in
+	$(AM_V_at) cp $< $@
+distclean-recursive distdir maintainer-clean-recursive: c++/Makefile
 endif
 
 libclamav_nocxx_la_SOURCES = bytecode_nojit.c

libclamav/Makefile.in

@@ -522,8 +522,9 @@ top_srcdir = @top_srcdir@
 AM_CPPFLAGS = -I$(top_srcdir) -I@srcdir@/nsis $(LTDLINCL) \
 	$(am__append_1)
 lib_LTLIBRARIES = $(am__append_3) libclamav.la
-EXTRA_DIST = $(am__append_4) regex/engine.c libclamav.map \
-	jsparse/generated/operators.h jsparse/generated/keywords.h \
+EXTRA_DIST = c++/Makefile.nollvm.in $(am__append_4) regex/engine.c \
+	libclamav.map jsparse/generated/operators.h \
+	jsparse/generated/keywords.h \
 	jsparse/future_reserved_words.list jsparse/keywords.list \
 	jsparse/special_keywords.list jsparse/operators.gperf
 @ENABLE_UNRAR_TRUE@libclamunrar_la_LDFLAGS = @TH_SAFE@ -version-info \
@@ -2252,6 +2253,9 @@ uninstall-am: uninstall-includeHEADERS uninstall-libLTLIBRARIES
 	tags tags-recursive uninstall uninstall-am \
 	uninstall-includeHEADERS uninstall-libLTLIBRARIES
 
+@ENABLE_LLVM_FALSE@c++/Makefile: c++/Makefile.nollvm.in
+@ENABLE_LLVM_FALSE@	$(AM_V_at) cp $< $@
+@ENABLE_LLVM_FALSE@distclean-recursive distdir maintainer-clean-recursive: c++/Makefile
 
 .PHONY: version.h.tmp
 version.c: version.h

libclamav/c++/Makefile.nollvm.in

@@ -0,0 +1,9 @@
+.PHONY: distdir distclean maintainer-clean
+distdir:
+	echo "make distdir requires --enable-llvm"
+	exit 1
+
+# nothing to do here, rules must exist for distclean to succeed
+distclean:
+	-rm -f Makefile
+maintainer-clean: