Retrieve linker flags for libftdi with pkg-config

Retrieve the proper linker flags for libftdi via pkg-config and fall
back if pkg-config isn't available or if it doesn't know libftdi.

Fix $LIBS and $FEATURE_LIBS to honor dependency order.

The original patch is from Jörg, it has been updated by Carl-Daniel to
work on the current tree and to have a fallback in case pkg-config is
not available or not working.

Corresponding to flashrom svn r762.
Signed-off-by: Jörg Mayer <jmayer@loplof.de>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Jörg Mayer <jmayer@loplof.de>

Makefile

@@ -120,10 +120,11 @@ FEATURE_CFLAGS += -D'SATASII_SUPPORT=1'
 OBJS += satasii.o
 endif
 
+FTDILIBS := $(shell pkg-config --libs libftdi 2>/dev/null || printf "%s" "-lftdi -lusb")
 ifeq ($(CONFIG_FT2232SPI), yes)
 # This is a totally ugly hack.
 FEATURE_CFLAGS += $(shell LC_ALL=C grep -q "FTDISUPPORT := yes" .features && printf "%s" "-D'FT2232_SPI_SUPPORT=1'")
-FEATURE_LIBS += $(shell LC_ALL=C grep -q "FTDISUPPORT := yes" .features && printf "%s" "-lftdi")
+FEATURE_LIBS += $(shell LC_ALL=C grep -q "FTDISUPPORT := yes" .features && printf "%s" "$(FTDILIBS)")
 OBJS += ft2232_spi.o
 endif
 
@@ -146,7 +147,7 @@ endif
 FEATURE_LIBS += $(shell LC_ALL=C grep -q "NEEDLIBZ := yes" .libdeps && printf "%s" "-lz")
 
 $(PROGRAM): $(OBJS)
-	$(CC) $(LDFLAGS) -o $(PROGRAM) $(OBJS) $(LIBS) $(FEATURE_LIBS)
+	$(CC) $(LDFLAGS) -o $(PROGRAM) $(OBJS) $(FEATURE_LIBS) $(LIBS)
 
 # TAROPTIONS reduces information leakage from the packager's system.
 # If other tar programs support command line arguments for setting uid/gid of
@@ -218,7 +219,7 @@ features: compiler
 		   echo "struct ftdi_context *ftdic = NULL;";	   \
 		   echo "int main(int argc, char **argv)"; \
 		   echo "{ return ftdi_init(ftdic); }"; ) > .featuretest.c )
-	@$(CC) $(CFLAGS) $(LDFLAGS) .featuretest.c -o .featuretest $(LIBS) -lftdi >/dev/null 2>&1 &&	\
+	@$(CC) $(CFLAGS) $(LDFLAGS) .featuretest.c -o .featuretest $(FTDILIBS) $(LIBS) >/dev/null 2>&1 &&	\
 		( echo "found."; echo "FTDISUPPORT := yes" >> .features.tmp ) ||	\
 		( echo "not found."; echo "FTDISUPPORT := no" >> .features.tmp )
 	@$(DIFF) -q .features.tmp .features >/dev/null 2>&1 && rm .features.tmp || mv .features.tmp .features