Use clang --driver-mode instead of guessing c++ compiler path

[beanz]

Summary

When building the LLDB test programs, if your CC is clang it actually isn't safe to make CXX a string replace of "clang -> clang++". This falls down on unix configurations if your compiler is clang-${version}.

A safer approach is to use the "--driver-mode=g++" option to tell clang to act like clang++.

[tfiala]

LGTM.

lldb/trunk/packages/Python/lldbsuite/test/make/Makefile.rules

ifneq "$(DYLIB_NAME)" ""
   else ifeq "$(OS)" "Windows_NT"
     DYLIB_FILENAME = $(DYLIB_NAME).dll
   else
     DYLIB_FILENAME = lib$(DYLIB_NAME).so
   endif
 endif
 
 # Function that returns the counterpart C++ compiler, given $(CC) as arg.
-cxx_compiler_notdir = $(if $(findstring clang,$(1)), \
-                           $(subst clang,clang++,$(1)), \
-                           $(if $(findstring icc,$(1)), \
-                                $(subst icc,icpc,$(1)), \
-                                $(if $(findstring llvm-gcc,$(1)), \
-                                     $(subst llvm-gcc,llvm-g++,$(1)), \
-                                     $(if $(findstring gcc,$(1)), \
-                                          $(subst gcc,g++,$(1)), \
-                                          $(subst cc,c++,$(1))))))
+cxx_compiler_notdir = $(if $(findstring icc,$(1)), \
+                                      $(subst cc,c++,$(1)))))
 cxx_compiler = $(if $(findstring /,$(1)),$(join $(dir $(1)), $(call cxx_compiler_notdir,$(notdir $(1)))),$(call cxx_compiler_notdir,$(1)))
 
+ifeq ($(findstring clang, $(cxx_compiler)), clang)
+    CXXFLAGS += --driver-mode=g++
+endif
+
 # Function that returns the C++ linker, given $(CC) as arg.
-cxx_linker_notdir = $(if $(findstring clang,$(1)), \
-                         $(subst clang,clang++,$(1)), \
-                         $(if $(findstring icc,$(1)), \
-                              $(subst icc,icpc,$(1)), \
-                              $(if $(findstring llvm-gcc,$(1)), \
-                                   $(subst llvm-gcc,llvm-g++,$(1)), \
-                                   $(if $(findstring gcc,$(1)), \
-                                        $(subst gcc,g++,$(1)), \
-                                        $(subst cc,c++,$(1))))))
+cxx_linker_notdir = $(if $(findstring icc,$(1)), \
+                                    $(subst cc,c++,$(1)))))
 cxx_linker = $(if $(findstring /,$(1)),$(join $(dir $(1)), $(call cxx_linker_notdir,$(notdir $(1)))),$(call cxx_linker_notdir,$(1)))
 
 ifneq "$(OS)" "Darwin"
     CLANG_OR_GCC := $(strip $(if $(findstring clang,$(CC)), \
                                  $(findstring clang,$(CC)), \
                                  $(if $(findstring gcc,$(CC)), \
                                       $(findstring gcc,$(CC)), \
                                       cc)))

 ifneq "$(strip $(DYLIB_OBJC_SOURCES))" ""
   DYLIB_OBJECTS +=$(strip $(DYLIB_OBJC_SOURCES:.m=.o))
 endif
 
 ifneq "$(strip $(DYLIB_CXX_SOURCES))" ""
     DYLIB_OBJECTS +=$(strip $(DYLIB_CXX_SOURCES:.cpp=.o))
     CXX = $(call cxx_compiler,$(CC))
     LD = $(call cxx_linker,$(CC))
+    LDFLAGS += --driver-mode=g++
 endif
 
 #----------------------------------------------------------------------
 # Check if we have a precompiled header
 #----------------------------------------------------------------------
 ifneq "$(strip $(PCH_CXX_SOURCE))" ""
     PCH_OUTPUT = $(PCH_CXX_SOURCE:.h=.h.pch)
     PCHFLAGS = -include $(PCH_CXX_SOURCE)
 endif
 
 #----------------------------------------------------------------------
 # Check if we have any C source files
 #----------------------------------------------------------------------
 ifneq "$(strip $(C_SOURCES))" ""
   OBJECTS +=$(strip $(C_SOURCES:.c=.o))
 endif
 
 #----------------------------------------------------------------------
 # Check if we have any C++ source files
 #----------------------------------------------------------------------
 ifneq "$(strip $(CXX_SOURCES))" ""
   OBJECTS +=$(strip $(CXX_SOURCES:.cpp=.o))
   CXX = $(call cxx_compiler,$(CC))
+  LDFLAGS += --driver-mode=g++
   LD = $(call cxx_linker,$(CC))
 endif
 
 #----------------------------------------------------------------------
 # Check if we have any ObjC source files
 #----------------------------------------------------------------------
 ifneq "$(strip $(OBJC_SOURCES))" ""
   OBJECTS +=$(strip $(OBJC_SOURCES:.m=.o))
   LDFLAGS +=-lobjc
 endif
 
 #----------------------------------------------------------------------
 # Check if we have any ObjC++ source files
 #----------------------------------------------------------------------
 ifneq "$(strip $(OBJCXX_SOURCES))" ""
   OBJECTS +=$(strip $(OBJCXX_SOURCES:.mm=.o))
   CXX = $(call cxx_compiler,$(CC))
   LD = $(call cxx_linker,$(CC))
+  LDFLAGS += --driver-mode=g++
   ifeq "$(findstring lobjc,$(LDFLAGS))" ""
     LDFLAGS +=-lobjc
   endif
 endif
 
 #----------------------------------------------------------------------
 # Check if we have any C source files for archive
 #----------------------------------------------------------------------