build: allow non-standard variations of linker -l/-L flags

This enables replacing the -l and -L flags used to specify the
just-built libraries when linking the tools and shared libs with
non-standard syntaxes.  System library flags are already handled
by the filtering mechanism in configure.
Signed-off-by: Mans Rullgard <mans@mansr.com>

Makefile

@@ -29,7 +29,7 @@ CCFLAGS     = $(CPPFLAGS) $(CFLAGS)
 ASFLAGS    := $(CPPFLAGS) $(ASFLAGS)
 YASMFLAGS  += $(IFLAGS:%=%/) -I$(SRC_PATH)/libavutil/x86/ -Pconfig.asm
 HOSTCCFLAGS = $(IFLAGS) $(HOSTCFLAGS)
-LDFLAGS    := $(ALLFFLIBS:%=-Llib%) $(LDFLAGS)
+LDFLAGS    := $(ALLFFLIBS:%=$(LD_PATH)lib%) $(LDFLAGS)
 
 define COMPILE
 	$(call $(1)DEP,$(1))

common.mak

@@ -11,7 +11,8 @@ OBJS      += $(OBJS-yes)
 FFLIBS    := $(FFLIBS-yes) $(FFLIBS)
 TESTPROGS += $(TESTPROGS-yes)
 
-FFEXTRALIBS := $(FFLIBS:%=-l%$(BUILDSUF)) $(EXTRALIBS)
+LDLIBS       = $(FFLIBS:%=%$(BUILDSUF))
+FFEXTRALIBS := $(LDLIBS:%=$(LD_LIB)) $(EXTRALIBS)
 
 EXAMPLES  := $(EXAMPLES:%=$(SUBDIR)%-example$(EXESUF))
 OBJS      := $(sort $(OBJS:%=$(SUBDIR)%))

configure

@@ -1785,6 +1785,8 @@ CC_C='-c'
 CC_E='-E -o $@'
 CC_O='-o $@'
 LD_O='-o $@'
+LD_LIB='-l%'
+LD_PATH='-L'
 HOSTCC_C='-c'
 HOSTCC_O='-o $@'
 HOSTLD_O='-o $@'
@@ -2132,7 +2134,8 @@ probe_cc(){
     pfx=$1
     _cc=$2
 
-    unset _type _ident _cc_c _cc_e _cc_o _ld_o _flags _cflags _ldflags
+    unset _type _ident _cc_c _cc_e _cc_o _flags _cflags
+    unset _ld_o _ldflags _ld_lib _ld_path
     unset _depflags _DEPCMD _DEPFLAGS
     _flags_filter=echo
 
@@ -2294,6 +2297,8 @@ ldflags_filter=$_flags_filter
 add_ldflags $_flags $_ldflags
 test "$cc_type" != "$ld_type" && add_ldflags $cc_ldflags
 LD_O=${_ld_o-$LD_O}
+LD_LIB=${_ld_lib-$LD_LIB}
+LD_PATH=${_ld_path-$LD_PATH}
 
 probe_cc hostld "$host_ld"
 host_ldflags_filter=$_flags_filter
@@ -3523,6 +3528,8 @@ AS_O=$AS_O
 CC_C=$CC_C
 CC_O=$CC_O
 LD_O=$LD_O
+LD_LIB=$LD_LIB
+LD_PATH=$LD_PATH
 DLLTOOL=$dlltool
 LDFLAGS=$LDFLAGS
 LDFLAGS-avserver=$AVSERVERLDFLAGS

libavformat/Makefile

@@ -379,4 +379,4 @@ TOOLS     = aviocat                                                     \
             pktdumper                                                   \
             probetest                                                   \
 
-$(SUBDIR)output-example$(EXESUF): ELIBS = -lswscale
+$(SUBDIR)output-example$(EXESUF): ELIBS = $(patsubst %,$(LD_LIB),swscale)

library.mak

@@ -35,7 +35,7 @@ install-libs-$(CONFIG_SHARED): install-lib$(NAME)-shared
 
 define RULES
 $(EXAMPLES) $(TESTPROGS) $(TOOLS): %$(EXESUF): %.o
-	$$(LD) $(LDFLAGS) $$(LD_O) $$^ -l$(FULLNAME) $(FFEXTRALIBS) $$(ELIBS)
+	$$(LD) $(LDFLAGS) $$(LD_O) $$^ $(FULLNAME:%=$(LD_LIB)) $(FFEXTRALIBS) $$(ELIBS)
 
 $(SUBDIR)$(SLIBNAME): $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
 	$(Q)cd ./$(SUBDIR) && $(LN_S) $(SLIBNAME_WITH_MAJOR) $(SLIBNAME)