fix build in case of spaces in path to make (#2619)

Makefile

@@ -138,10 +138,10 @@ endif
 all: lib/libxgboost.a $(XGBOOST_DYLIB) xgboost
 
 $(DMLC_CORE)/libdmlc.a: $(wildcard $(DMLC_CORE)/src/*.cc $(DMLC_CORE)/src/*/*.cc)
-	+ cd $(DMLC_CORE); $(MAKE) libdmlc.a config=$(ROOTDIR)/$(config); cd $(ROOTDIR)
+	+ cd $(DMLC_CORE); "$(MAKE)" libdmlc.a config=$(ROOTDIR)/$(config); cd $(ROOTDIR)
 
 $(RABIT)/lib/$(LIB_RABIT): $(wildcard $(RABIT)/src/*.cc)
-	+ cd $(RABIT); $(MAKE) lib/$(LIB_RABIT) USE_SSE=$(USE_SSE); cd $(ROOTDIR)
+	+ cd $(RABIT); "$(MAKE)" lib/$(LIB_RABIT) USE_SSE=$(USE_SSE); cd $(ROOTDIR)
 
 jvm: jvm-packages/lib/libxgboost4j.so
 
@@ -233,8 +233,8 @@ clean:
 	cd R-package/src; $(RM) -rf rabit src include dmlc-core amalgamation *.so *.dll; cd $(ROOTDIR)
 
 clean_all: clean
-	cd $(DMLC_CORE); $(MAKE) clean; cd $(ROOTDIR)
-	cd $(RABIT); $(MAKE) clean; cd $(ROOTDIR)
+	cd $(DMLC_CORE); "$(MAKE)" clean; cd $(ROOTDIR)
+	cd $(RABIT); "$(MAKE)" clean; cd $(ROOTDIR)
 
 doxygen:
 	doxygen doc/Doxyfile