[Makefile]: Add conditional to not build the macos gui if it's not th…

…e xcode version of xcodebuild

src/Makefile.OCaml

@@ -51,6 +51,10 @@ OCAMLLIBDIR:=$(shell $(OCAMLC) -config-var standard_library)
 #
 OCAMLFIND := $(shell command -v ocamlfind 2> /dev/null)
 
+# Any invocation of the non-Xcode version of xcodebuild will trigger an error message
+# and an non 0 exit code. 
+XCODEBUILD := $(shell xcodebuild -version > /dev/null; echo $$?)
+
 ifdef OCAMLFIND
   ifneq ($(strip $(shell $(OCAMLFIND) query lablgtk3 2> /dev/null)),)
     HAS_LABLGTK3=true
@@ -72,7 +76,12 @@ endif
 
 .PHONY: macuimaybe
 ifeq ($(OSARCH), Darwin)
-  macuimaybe: macui
+  ifeq ($(XCODEBUILD), 0)
+    macuimaybe: macui
+  else
+    macuimaybe:
+      $(info Not the xcode version of xcodebuild, macOS native GUI can not be build.)
+    endif
 else
   macuimaybe:
 	$(info Not on macOS. macOS native GUI will not be built.)