libpayload: Move .xcompile into $(obj)

Keep libpayload's xcompile in its build dir. While we are at it,
align things with the top-level version.

Having `.xcompile` in a central place led to race conditions when
multiple payloads try to build their own libpayloads in parallel.

Change-Id: I504e1862db79b368289867f7568c9169f27a1549
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47651
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/payloads/libpayload/Makefile b/payloads/libpayload/Makefile
index b5687c3..0b08c70 100644
--- a/payloads/libpayload/Makefile
+++ b/payloads/libpayload/Makefile
@@ -118,6 +118,11 @@
 endif
 endif
 
+xcompile ?= $(obj)/xcompile
+$(xcompile): $(top)/../../util/xcompile/xcompile
+	$< $(XGCCPATH) > $@.tmp
+	\mv -f $@.tmp $@ 2> /dev/null
+
 ifeq ($(NOCOMPILE),1)
 include $(TOPLEVEL)/Makefile.inc
 real-all: config
@@ -126,13 +131,17 @@
 
 # in addition to the dependency below, create the file if it doesn't exist
 # to silence stupid warnings about a file that would be generated anyway.
-$(if $(wildcard .xcompile)$(NOCOMPILE),,$(eval $(shell $(top)/../../util/xcompile/xcompile $(XGCCPATH) > .xcompile)))
+$(if $(wildcard $(xcompile)),,$(shell	\
+	mkdir -p $(dir $(xcompile)) &&	\
+	$(top)/../../util/xcompile/xcompile $(XGCCPATH) > $(xcompile) || rm -f $(xcompile)))
 
-.xcompile: $(top)/../../util/xcompile/xcompile
-	$< $(XGCCPATH) > $@.tmp
-	\mv -f $@.tmp $@ 2> /dev/null
+include $(xcompile)
 
--include .xcompile
+ifneq ($(XCOMPILE_COMPLETE),1)
+$(shell rm -f $(xcompile))
+$(error $(xcompile) deleted because it's invalid. \
+	Restarting the build should fix that, or explain the problem)
+endif
 
 CC := $(CC_$(ARCH-y))
 AS := $(AS_$(ARCH-y))
@@ -294,7 +303,7 @@
 	rm -rf $(DOXYGEN_OUTPUT_DIR)
 
 clean-for-update: doxygen-clean clean-for-update-target
-	rm -f $(allobjs) .xcompile
+	rm -f $(allobjs) $(xcompile)
 	rm -f $(DEPENDENCIES)
 	rmdir -p $(alldirs) 2>/dev/null >/dev/null || true
 
diff --git a/payloads/libpayload/Makefile.inc b/payloads/libpayload/Makefile.inc
index 6188dde..6835b84 100644
--- a/payloads/libpayload/Makefile.inc
+++ b/payloads/libpayload/Makefile.inc
@@ -121,7 +121,7 @@
 	install -m 755 bin/lpas $(DESTDIR)/libpayload/bin
 	install -m 644 bin/lp.functions $(DESTDIR)/libpayload/bin
 	install -m 644 $(DOTCONFIG) $(DESTDIR)/libpayload/libpayload.config
-	install -m 755 .xcompile $(DESTDIR)/libpayload/libpayload.xcompile
+	install -m 755 $(xcompile) $(DESTDIR)/libpayload/libpayload.xcompile
 
 clean-for-update-target:
 	rm -f $(addsuffix .a,$(addprefix $(obj)/,$(libraries))) $(obj)/libpayload.a
diff --git a/payloads/libpayload/sample/Makefile b/payloads/libpayload/sample/Makefile
index eb70af9..637e45d 100644
--- a/payloads/libpayload/sample/Makefile
+++ b/payloads/libpayload/sample/Makefile
@@ -28,7 +28,7 @@
 
 # Sample libpayload Makefile.
 include ../.config
-include ../.xcompile
+include ../build/xcompile
 
 ARCH-$(CONFIG_LP_ARCH_ARM)   := arm
 ARCH-$(CONFIG_LP_ARCH_X86)   := x86_32