Enable out-of-tree builds without modifying the source tree.
Out-of-tree builds are required by build frameworks such as OpenEmbedded.

Signed-off-by: Maxin John <maxin.john@gmail.com>
---
 Makefile | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/Makefile b/Makefile
index 2652fac4e6ee..fbbc3042cd37 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,8 @@
 MAKEFLAGS += --no-print-directory
 
+SRCDIR := $(dir $(lastword $(MAKEFILE_LIST)))
+VPATH := $(SRCDIR)
+
 PREFIX ?= /usr
 SBINDIR ?= $(PREFIX)/sbin
 MANDIR ?= $(PREFIX)/share/man
@@ -21,7 +24,11 @@ CFLAGS += -D__SANE_USERSPACE_TYPES__
 CFLAGS += $(CFLAGS_EVAL)
 CFLAGS += $(EXTRA_CFLAGS)
 
-_OBJS := $(sort $(patsubst %.c,%.o,$(wildcard *.c)))
+CPPFLAGS += -I$(SRCDIR)
+CPPFLAGS += -I.
+
+_SRCS := $(wildcard $(SRCDIR)/*.c)
+_OBJS := $(sort $(patsubst $(SRCDIR)/%.c,%.o,$(_SRCS)))
 VERSION_OBJS := $(filter-out version.o, $(_OBJS))
 OBJS := $(VERSION_OBJS) version.o
 
@@ -92,16 +99,18 @@ endif
 
 all: $(ALL)
 
-version.c: version.sh $(patsubst %.o,%.c,$(VERSION_OBJS)) nl80211.h iw.h Makefile \
-		$(wildcard .git/index .git/refs/tags)
+version.c: $(SRCDIR)/version.sh \
+	$(patsubst %.o,$(SRCDIR)/%.c,$(VERSION_OBJS)) \
+	$(SRCDIR)/nl80211.h $(SRCDIR)/iw.h $(SRCDIR)/Makefile \
+	$(wildcard $(SRCDIR)/.git/index $(SRCDIR)/.git/refs/tags)
 	@$(NQ) ' GEN ' $@
-	$(Q)./version.sh $@
+	$(Q)$(SRCDIR)/version.sh $@
 
-nl80211-commands.inc: nl80211.h
+nl80211-commands.inc: $(SRCDIR)/nl80211.h
 	@$(NQ) ' GEN ' $@
-	$(Q)sed 's%^\tNL80211_CMD_%%;t n;d;:n s%^\([^=]*\),.*%\t[NL80211_CMD_\1] = \"\L\1\",%;t;d' nl80211.h | grep -v "reserved" > $@
+	$(Q)sed 's%^\tNL80211_CMD_%%;t n;d;:n s%^\([^=]*\),.*%\t[NL80211_CMD_\1] = \"\L\1\",%;t;d' $(SRCDIR)/nl80211.h | grep -v "reserved" > $@
 
-%.o: %.c iw.h nl80211.h nl80211-commands.inc
+%.o: %.c $(SRCDIR)/iw.h $(SRCDIR)/nl80211.h nl80211-commands.inc
 	@$(NQ) ' CC  ' $@
 	$(Q)$(CC) $(CFLAGS) $(CPPFLAGS) -c -o $@ $<
 
-- 
2.47.3