make clean fix for eclipse / mcuxpreso projects with generated makefiles

makefile.targets

## section only for 'clean' target
# CDT's generated makefile contains a clean target containing so many files, it can't be executed on windows
# this is a workaround to invoke a per file delete instead, without the need to switch to writing the makefiles
# manualy.

# if make is called with 'clean' as the first argument, prepare some special workaround to limit command line length 
ifeq (clean,$(firstword $(MAKECMDGOALS)))


# implement a string length function
!chars := A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
!chars += a b c d e f g h i j k l m n o p q r s t u v w x y z
!chars += 0 1 2 3 4 5 6 7 8 9
!chars += ` ~ ! @ \# $$ % ^ & * ( ) - _ = +
!chars += { } [ ] \ : ; ' " < > , . / ? |

!empty :=
!space := $(!empty) $(!empty)

# actual function, calling to an external tool is not possible...
!strlen = $(strip $(eval !strlen_tmp := $(subst $(!space),x,$1))$(foreach a,$(!chars),$(eval !strlen_tmp := $$(subst $$a,x,$(!strlen_tmp))))$(eval !strlen_tmp := $(subst x,x ,$(!strlen_tmp)))$(words $(!strlen_tmp)))

# calculate the length without leaving make
# uses the command and arguments from the 'clean: ' target to aproximate the length
!rmcmdlen := $(call !strlen, $(RM) $(EXECUTABLES) $(OBJS) $(C_DEPS))

# use the shell to check if the 32k limit might be reached
!rmistolong := $(shell echo $$(($(!rmcmdlen) > 32000 )) )

# use the workaround if it is to long, to make it work. if not, use the default clean
ifeq (1,${!rmistolong})

# do not run any target exept for ones with + commands, this will skip 'clean' (and all other targets) 
# and assume they are already done
MAKEFLAGS+=  -t


# get the files that exist and really need to be removed
cleanfiles := $(strip $(foreach f, $(EXECUTABLES) $(OBJS) $(C_DEPS) *.axf ,$(wildcard $(f))))

# create a .clean target name for them
cleantargets:=$(patsubst %,%.clean,$(cleanfiles))

# they do not exist as files on disk
.PHONY: $(cleantargets)

# add targets as an order dependency to 'clean' to get them executed prior to 'clean'
clean: | $(cleantargets) $(info make: Using 'clean' workaround from 'makefile.targets', command line length is over 32k. )

# add a %.clean pattern rule for each file, with a + to force execution 
# the + prefixed commands are even executed weth -t is active
$(cleantargets): %.clean : %
	+@${RM} $<

# make will remove all existing files prior accepting it needs nothing to do for 'clean'
endif
endif
## end of section only for 'clean' target,