Makefile

CXX ?= c++
build_dir := $(shell which $(CXX))
tmp := "case $$(readlink -f $(build_dir)) in *icecc) which $${ICECC_CXX:-g++};; *) echo $(build_dir);; esac"
build_dir := $(shell sh -c $(tmp))
build_dir := $(realpath $(build_dir))
build_dir := build-$(subst /,-,$(build_dir:/%=%)$(CXXFLAGS))

all:
%:: $(build_dir)/CMakeCache.txt
	$(MAKE) --no-print-directory -C "$(build_dir)" $(MAKECMDGOALS)

$(build_dir)/CMakeCache.txt:
	@test -n "$(build_dir)"
	@mkdir -p "$(build_dir)"
	@test -e "$(build_dir)/CMakeCache.txt" || cmake -H. -B"$(build_dir)"

print_build_dir:
	@echo "$(PWD)/$(build_dir)"

clean_builddir:
	rm -rf "$(build_dir)"

# the following rule works around %:: grabbing the Makefile rule and thus stops it from running every time
Makefile:
	@true

.PHONY: print_build_dir clean_builddir