Added a rule to the Makefile to build libwebm as a shared

library.

I'm building two different object files now: the ones for
libwebm.a are compiled normally (*_a.o), and the ones for
libwebm.so are compiled with -fPIC and linked with -shared
(*_so.o).

Change-Id: I76471ab225a006c7e169bc0d69df9a0731ff6681

Makefile

@@ -1,29 +1,43 @@
-CXX      := g++
-CXXFLAGS := -W -Wall -g
-LIBWEBM  := libwebm.a
-WEBMOBJS := mkvparser.o mkvreader.o mkvmuxer.o mkvmuxerutil.o mkvwriter.o
-OBJECTS1 := sample.o
-OBJECTS2 := sample_muxer.o
-OBJECTS3 := dumpvtt.o vttreader.o webvttparser.o
-INCLUDES := -I.
-EXES     := samplemuxer sample dumpvtt
+CXX       := g++
+CXXFLAGS  := -W -Wall -g
+LIBWEBMA  := libwebm.a
+LIBWEBMSO := libwebm.so
+WEBMOBJS  := mkvparser.o mkvreader.o mkvmuxer.o mkvmuxerutil.o mkvwriter.o
+OBJSA     := $(WEBMOBJS:.o=_a.o)
+OBJSSO    := $(WEBMOBJS:.o=_so.o)
+OBJECTS1  := sample.o
+OBJECTS2  := sample_muxer.o
+OBJECTS3  := dumpvtt.o vttreader.o webvttparser.o
+INCLUDES  := -I.
+EXES      := samplemuxer sample dumpvtt
 
 all: $(EXES)
 
-sample: sample.o $(LIBWEBM)
+sample: sample.o $(LIBWEBMA)
 	$(CXX) $^ -o $@
 
-samplemuxer: sample_muxer.o $(LIBWEBM)
+samplemuxer: sample_muxer.o $(LIBWEBMA)
 	$(CXX) $^ -o $@
 
 dumpvtt: $(OBJECTS3)
 	$(CXX) $^ -o $@
 
-libwebm.a: $(WEBMOBJS)
+shared: $(LIBWEBMSO)
+
+libwebm.a: $(OBJSA)
 	$(AR) rcs $@ $^
 
+libwebm.so: $(OBJSSO)
+	$(CXX) $(CXXFLAGS) -shared $(OBJSSO) -o $(LIBWEBMSO)
+
 %.o: %.cpp
 	$(CXX) -c $(CXXFLAGS) $(INCLUDES) $< -o $@
 
+%_a.o: %.cpp
+	$(CXX) -c $(CXXFLAGS) $(INCLUDES) $< -o $@
+
+%_so.o: %.cpp
+	$(CXX) -c $(CXXFLAGS) -fPIC $(INCLUDES) $< -o $@
+
 clean:
-	$(RM) -f $(OBJECTS1) $(OBJECTS2) $(OBJECTS3) $(WEBMOBJS) $(LIBWEBM) $(EXES) Makefile.bak
+	$(RM) -f $(OBJECTS1) $(OBJECTS2) $(OBJECTS3) $(OBJSA) $(OBJSSO) $(LIBWEBMA) $(LIBWEBMSO) $(EXES) Makefile.bak