[NaCl SDK] Print nice error if host build can't find gcc or cl.exe

native_client_sdk/src/tools/common.mk

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 #
 # GNU Make based build file.  For details on GNU Make see:
 #   http://www.gnu.org/software/make/manual/make.html
 #
 #
 
@@ skipping 51 matching lines @@
 export CYGWIN
 
 
 #
 # Alias for standard POSIX file system commands
 #
 CP:=python $(NACL_SDK_ROOT)/tools/oshelpers.py cp
 MKDIR:=python $(NACL_SDK_ROOT)/tools/oshelpers.py mkdir
 MV:=python $(NACL_SDK_ROOT)/tools/oshelpers.py mv
 RM:=python $(NACL_SDK_ROOT)/tools/oshelpers.py rm
+WHICH:=python $(NACL_SDK_ROOT)/tools/oshelpers.py which
 
 
 #
 # Compute path to requested NaCl Toolchain
 #
 OSNAME:=$(shell python $(NACL_SDK_ROOT)/tools/getos.py)
 TC_PATH:=$(abspath $(NACL_SDK_ROOT)/toolchain)
 
 
 
@@ skipping 18 matching lines @@
 all_$(1):
         +$(MAKE) TOOLCHAIN=$(1)
 TOOLCHAIN_LIST+=all_$(1)
 endef
 
 
 #
 # The target for all versions
 #
 USABLE_TOOLCHAINS=$(filter $(OSNAME) newlib glibc pnacl,$(VALID_TOOLCHAINS))
+
+ifeq (1,$(NO_HOST_BUILDS))
+USABLE_TOOLCHAINS:=$(filter-out $(OSNAME),$(USABLE_TOOLCHAINS))

[noelallen_use_chromium, 2013/02/09 00:55:57]

$(warning Skipping host builds)

+endif
+
+.PHONY: CHECK_FOR_CL_EXE
+CHECK_FOR_CL_EXE:
+ifneq (,$(findstring win,$(USABLE_TOOLCHAINS)))
+ifeq (,$(findstring cl.exe,$(shell $(WHICH) cl.exe)))
+        $(warning To skip the host build use:)
+        $(warning "make all_versions NO_HOST_BUILDS=1")
+        $(error Unable to find cl.exe in PATH while building Windows host build)
+endif
+endif

[noelallen_use_chromium, 2013/02/09 00:55:57]

Won't this generate an empty target warning/error for non windows?

+
 $(foreach tool,$(USABLE_TOOLCHAINS),$(eval $(call TOOLCHAIN_RULE,$(tool),$(dep))))
-all_versions: $(TOOLCHAIN_LIST)
+
+.PHONY: all_versions
+all_versions: CHECK_FOR_CL_EXE $(TOOLCHAIN_LIST)
 
 #
 # Target to remove temporary files
 #
 .PHONY: clean
 clean:
         $(RM) $(TARGET).nmf
         $(RM) -fr $(TOOLCHAIN)
 
 
@@ skipping 134 matching lines @@
 
 SYSARCH=$(shell python $(NACL_SDK_ROOT)/tools/getos.py --chrome)
 GDB_ARGS+=-D $(TC_PATH)/$(OSNAME)_x86_$(TOOLCHAIN)/bin/$(SYSARCH)-nacl-gdb
 GDB_ARGS+=-D $(CURDIR)/$(OUTDIR)/$(TARGET)_$(SYSARCH).nexe
 
 DEBUG: CHECK_FOR_CHROME all
         $(RUN_PY) $(GDB_ARGS) \
             -C $(CURDIR) -P $(PAGE) $(addprefix -E ,$(CHROME_ENV)) -- \
             $(CHROME_PATH) $(CHROME_ARGS) --enable-nacl-debug \
             --register-pepper-plugins="$(PPAPI_DEBUG),$(PPAPI_RELEASE)"