make use of make variable CURDIR instead of calling pwd

make already provides the current working directory in a variable, so make
use of it instead of forking a shell. Also replace usage of PWD by
CURDIR. PWD is provided by most shells, but not all, so this makes the
build system more robust.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Michal Marek <mmarek@suse.com>

samples/bpf/Makefile

@@ -119,10 +119,10 @@ CLANG ?= clang
 
 # Trick to allow make to be run from this directory
 all:
-	$(MAKE) -C ../../ $$PWD/
+	$(MAKE) -C ../../ $(CURDIR)/
 
 clean:
-	$(MAKE) -C ../../ M=$$PWD clean
+	$(MAKE) -C ../../ M=$(CURDIR) clean
 	@rm -f *~
 
 # Verify LLVM compiler tools are available and bpf target is supported by llc

samples/connector/Makefile

@@ -13,4 +13,4 @@ HOSTCFLAGS_ucon.o += -I$(objtree)/usr/include
 all: modules
 
 modules clean:
-	$(MAKE) -C ../.. SUBDIRS=$(PWD) $@
+	$(MAKE) -C ../.. SUBDIRS=$(CURDIR) $@