build: Include HEADERS-yes in the HEADERS variable

This makes sure the previously always installed public header
lzo.h is installed if the LZO functionality is enabled.
Signed-off-by: Martin Storsjö <martin@martin.st>

Makefile

@@ -102,7 +102,7 @@ config.h: .config
 	@-tput sgr0 2>/dev/null
 
 SUBDIR_VARS := CLEANFILES EXAMPLES FFLIBS HOSTPROGS TESTPROGS TOOLS      \
-               ARCH_HEADERS BUILT_HEADERS SKIPHEADERS                    \
+               HEADERS ARCH_HEADERS BUILT_HEADERS SKIPHEADERS            \
                ARMV5TE-OBJS ARMV6-OBJS ARMVFP-OBJS NEON-OBJS             \
                ALTIVEC-OBJS VIS-OBJS                                     \
                MMX-OBJS YASM-OBJS                                        \

common.mak

@@ -23,6 +23,7 @@ HOSTPROGS := $(HOSTPROGS:%=$(SUBDIR)%$(HOSTEXESUF))
 TOOLS     += $(TOOLS-yes)
 TOOLOBJS  := $(TOOLS:%=tools/%.o)
 TOOLS     := $(TOOLS:%=tools/%$(EXESUF))
+HEADERS   += $(HEADERS-yes)
 
 DEP_LIBS := $(foreach NAME,$(FFLIBS),lib$(NAME)/$($(CONFIG_SHARED:yes=S)LIBNAME))