Clean up STP src

The SNAME is exported in the general stp Makefile. The symbolic link is created there too.
Remove both actions from the special case as they are handled in the general case.

src/vendor/stp/src/Makefile

@@ -14,13 +14,7 @@ else
 CP = cp -df
 endif
 
-ifeq ($(OSTYPE), Darwin)
-LIBRARIES=lib/libstp.dylib
-SNAME = libstp.dylib
-else
-LIBRARIES=lib/libstp.so.1 lib/libstp.so
-SNAME = libstp.so.1
-endif
+LIBRARIES=lib/$(SNAME)
 
 .PHONY: all
 all: $(LIBRARIES)
@@ -72,12 +66,6 @@ lib/$(SNAME):  c_interface/c_interface.o \
 	@# We use --whole-archive to ensure that all symbols in to-sat are used
 	$(CXX) $(CFLAGS) $(SHAREDFLAG)  -Wl,$(SONAMEFLAG),$(SNAME) -o $@ $(LIBCCARGS)
 
-ifneq ($(OSTYPE), Darwin)
-lib/libstp.so: lib/libstp.so.1
-	-rm -f $@
-	(cd lib; ln -s libstp.so.1 libstp.so)
-endif
-
 
 # During the build of AST some classes are built that most of the other
 # classes depend upon. So in a parallel make, AST should be made first.