cmake: correct uninitialized vars

CMakeLists.txt

@@ -223,9 +223,6 @@ if(WITH_PYTHON_MODULE)
 	set(WITH_HEADLESS ON)
 endif()
 
-# remove old vars
-unset(WITH_INSTALL CACHE)
-
 TEST_SSE_SUPPORT()
 
 #-----------------------------------------------------------------------------
@@ -234,6 +231,9 @@ TEST_SSE_SUPPORT()
 # linux only, not cached
 set(WITH_BINRELOC OFF)
 
+# MAXOSX only, set to avoid uninitialized 
+set(EXETYPE "")
+
 # these are added to later on.
 set(C_WARNINGS "")
 set(CXX_WARNINGS "")