Build: HOST_CXX -> USE_HOST_CXX

Allow HOST_CXX to be passed to make which will be the actual host
C++ compiler used, such as 'make HOST_CXX=clang++'.

AK/Tests/Makefile

@@ -17,7 +17,7 @@ APPS = ${SRCS:.cpp=}
 
 EXTRA_CLEAN = $(APPS) *.o
 
-HOST_CXX = 1
+USE_HOST_CXX = 1
 
 include ../../Makefile.common
 

DevTools/FormCompiler/Makefile

@@ -1,4 +1,4 @@
-HOST_CXX = 1
+USE_HOST_CXX = 1
 
 PROGRAM = FormCompiler
 

DevTools/IPCCompiler/Makefile

@@ -1,4 +1,4 @@
-HOST_CXX = 1
+USE_HOST_CXX = 1
 
 PROGRAM = IPCCompiler
 

Libraries/LibHTML/CodeGenerators/Generate_CSS_PropertyID_cpp/Makefile

@@ -1,4 +1,4 @@
-HOST_CXX = 1
+USE_HOST_CXX = 1
 
 PROGRAM = Generate_CSS_PropertyID_cpp
 

Libraries/LibHTML/CodeGenerators/Generate_CSS_PropertyID_h/Makefile

@@ -1,4 +1,4 @@
-HOST_CXX = 1
+USE_HOST_CXX = 1
 
 PROGRAM = Generate_CSS_PropertyID_h
 

Makefile.common

@@ -22,12 +22,16 @@ INCLUDE_FLAGS += \
 
 VERBOSE = 0
 
-ifneq ($(HOST_CXX),)
+ifneq ($(USE_HOST_CXX),)
     ifeq '' '$(findstring clang++,$(CXX))'
         C_WARNING_FLAGS += -Wno-unknown-warning-option
         CXX_WARNING_FLAGS += -Wno-unknown-warning-option
     endif
-    CXX = $(PRE_CXX) g++
+    ifeq ($(HOST_CXX),)
+        CXX = $(PRE_CXX) g++
+    else
+        CXX = $(HOST_CXX)
+    endif
     AS = as
     LINK = ld
     OBJ_SUFFIX ?= .host