[shotwell] build: Speed up parallel builds

[Jens Georg <jensgeorg src gnome org>]

commit c48bf5d4231adbaff972cdc266b42aa1402912c7
Author: Jens Georg <mail jensge org>
Date:   Tue Apr 19 21:32:51 2016 +0200

    build: Speed up parallel builds
    
    Plugins were compiled several times because make did not get the dependencies
    right.
    
    Signed-off-by: Jens Georg <mail jensge org>

 plugins/Makefile.plugin.mk |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/plugins/Makefile.plugin.mk b/plugins/Makefile.plugin.mk
index 317aac5..03df7b0 100644
--- a/plugins/Makefile.plugin.mk
+++ b/plugins/Makefile.plugin.mk
@@ -52,11 +52,11 @@ all: $(PLUGIN).so
 $(CFILES): .stamp
        @
 
-$(OFILES): %.o: %.c $(CFILES)
-       $(CC) -c $(CFLAGS) $(DEFINES) -I../.. $(CFILES)
+.c.o:
+       $(CC) -c $(CFLAGS) $(DEFINES) -I../.. $<
 
 $(PLUGIN).so: $(OFILES)
-       $(CC) $(CFLAGS) $(LDFLAGS) -shared $(OFILES) $(LIBS) -o $@
+       $(CC) $(LDFLAGS) -shared $(OFILES) $(LIBS) -o $@
 
 .PHONY: cleantemps
 cleantemps: