cmake,LLVM: better xcross configuration

DRY some variables, and pass others along better

Make.inc

@@ -378,8 +378,10 @@ ifeq ($(XC_HOST),)
 CROSS_COMPILE:=
 # delayed expansion of $(CC), since it won't be computed until later
 HOSTCC = $(CC)
+HOSTCXX = $(CXX)
 else
 HOSTCC ?= gcc
+HOSTCXX ?= g++
 OPENBLAS_DYNAMIC_ARCH := 1
 override CROSS_COMPILE:=$(XC_HOST)-
 ifneq (,$(findstring mingw,$(XC_HOST)))

deps/llvm.mk

@@ -131,12 +131,12 @@ LLVM_CMAKE += -DLLVM_ENABLE_ASSERTIONS:BOOL=ON
 endif # LLVM_ASSERTIONS
 ifeq ($(OS), WINNT)
 LLVM_CPPFLAGS += -D__USING_SJLJ_EXCEPTIONS__ -D__CRT__NO_INLINE
-ifneq ($(BUILD_OS),WINNT)
-LLVM_CMAKE += -DCROSS_TOOLCHAIN_FLAGS_NATIVE=-DCMAKE_TOOLCHAIN_FILE=$(SRCDIR)/NATIVE.cmake
-endif # BUILD_OS != WINNT
 endif # OS == WINNT
+ifneq ($(HOSTCC),$(CC))
+LLVM_CMAKE += -DCROSS_TOOLCHAIN_FLAGS_NATIVE="-DCMAKE_C_COMPILER=$$(which $(HOSTCC));-DCMAKE_CXX_COMPILER=$$(which $(HOSTCXX))"
+endif
 ifeq ($(OS), emscripten)
-LLVM_CMAKE += -DCMAKE_TOOLCHAIN_FILE=$(EMSCRIPTEN)/cmake/Modules/Platform/Emscripten.cmake -DCROSS_TOOLCHAIN_FLAGS_NATIVE=-DCMAKE_TOOLCHAIN_FILE=$(SRCDIR)/NATIVE.cmake -DLLVM_INCLUDE_TOOLS=OFF -DLLVM_BUILD_TOOLS=OFF -DLLVM_INCLUDE_TESTS=OFF -DLLVM_ENABLE_THREADS=OFF -DLLVM_BUILD_UTILS=OFF
+LLVM_CMAKE += -DCMAKE_TOOLCHAIN_FILE=$(EMSCRIPTEN)/cmake/Modules/Platform/Emscripten.cmake -DLLVM_INCLUDE_TOOLS=OFF -DLLVM_BUILD_TOOLS=OFF -DLLVM_INCLUDE_TESTS=OFF -DLLVM_ENABLE_THREADS=OFF -DLLVM_BUILD_UTILS=OFF
 endif # OS == emscripten
 ifeq ($(USE_LLVM_SHLIB),1)
 # NOTE: we could also --disable-static here (on the condition we link tools

deps/tools/common.mk

@@ -35,14 +35,12 @@ CMAKE_COMMON += -DCMAKE_CXX_COMPILER="$(CXX_BASE)"
 ifneq ($(strip $(CMAKE_CXX_ARG)),)
 CMAKE_COMMON += -DCMAKE_CXX_COMPILER_ARG1="$(CMAKE_CXX_ARG)"
 endif
-CMAKE_COMMON += -DCMAKE_LINKER="$(shell which $(LD))" -DCMAKE_AR="$(shell which $(AR))" -DCMAKE_RANLIB="$(shell which $(RANLIB))"
+CMAKE_COMMON += -DCMAKE_LINKER="$$(which $(LD))" -DCMAKE_AR="$$(which $(AR))" -DCMAKE_RANLIB="$$(which $(RANLIB))"
 
 ifeq ($(OS),WINNT)
 CMAKE_COMMON += -DCMAKE_SYSTEM_NAME=Windows
-ifneq ($(BUILD_OS),WINNT)
 CMAKE_COMMON += -DCMAKE_RC_COMPILER="$$(which $(CROSS_COMPILE)windres)"
 endif
-endif
 
 # For now this is LLVM specific, but I expect it won't be in the future
 ifeq ($(CMAKE_GENERATOR),Ninja)