make openmp flags universal for gcc, icc, and clang

clang: http://clang-omp.github.io/

Author: pdknsk

Makefile

@@ -79,12 +79,7 @@ lib/libimagequant.a::
 	$(MAKE) -C lib static
 
 openmp::
-ifeq ($(CC), icc)
-	$(MAKE) CFLAGSADD="$(CFLAGSADD) -openmp" OPENMPFLAGS=-openmp -j8 $(MKFLAGS)
-else
-	$(MAKE) CFLAGSADD="$(CFLAGSADD) -fopenmp" OPENMPFLAGS="-Bstatic -lgomp" -j8 $(MKFLAGS)
-endif
-
+	$(MAKE) CFLAGSADD="$(CFLAGSADD) -fopenmp" OPENMPFLAGS="-Bstatic -fopenmp" -j8 $(MKFLAGS)
 
 $(BIN): $(OBJS) lib/libimagequant.a
 	$(CC) $(OBJS) $(LDFLAGS) $(OPENMPFLAGS) $(FRAMEWORKS) -o $@

lib/Makefile

@@ -41,11 +41,7 @@ dll:
 	$(MAKE) CFLAGSADD="-DLIQ_EXPORT='__declspec(dllexport)'" $(DLL)
 
 openmp::
-ifeq ($(CC), icc)
-	$(MAKE) CFLAGSADD=-openmp OPENMPFLAGS=-openmp -j8
-else
-	$(MAKE) CFLAGSADD=-fopenmp OPENMPFLAGS="-Bstatic -lgomp" -j8
-endif
+	$(MAKE) CFLAGSADD=-fopenmp OPENMPFLAGS="-Bstatic -fopenmp" -j8
 
 $(DLL) $(DLLIMP): $(OBJS)
 	$(CC) -fPIC -shared -o $(DLL) $(OBJS) $(LDFLAGS) -Wl,--out-implib,$(DLLIMP),--output-def,$(DLLDEF)