Add -latomic to all target builds

Projects using stdatomic.h needs libatomic.a in case compiler can't
expand all __atomic* intrinsics. eg, __atomic_is_lock_free in
armeabi/mips.

Adding libatomic.a globally makes more sense than adding
"LOCAL_LDLIB += -latomic " in each project including <stdatomic.h>.
Projects don't need atomic operations won't get redundant DT_NEEDED
entry because libatomic.a is not a shared library.

Change-Id: I81dbf524544c848e667e18ab5eeabff75b5063ef
diff --git a/core/combo/TARGET_linux-x86.mk b/core/combo/TARGET_linux-x86.mk
index 5bd6d7e..bc13fb9 100644
--- a/core/combo/TARGET_linux-x86.mk
+++ b/core/combo/TARGET_linux-x86.mk
@@ -60,6 +60,8 @@
 ifneq ($(wildcard $($(combo_2nd_arch_prefix)TARGET_CC)),)
 $(combo_2nd_arch_prefix)TARGET_LIBGCC := \
 	$(shell $($(combo_2nd_arch_prefix)TARGET_CC) -m32 -print-file-name=libgcc.a)
+$(combo_2nd_arch_prefix)TARGET_LIBATOMIC := \
+	$(shell $($(combo_2nd_arch_prefix)TARGET_CC) -m32 -print-file-name=libatomic.a)
 target_libgcov := $(shell $($(combo_2nd_arch_prefix)TARGET_CC) $($(combo_2nd_arch_prefix)TARGET_GLOBAL_CFLAGS) \
 	-print-file-name=libgcov.a)
 endif
@@ -195,6 +197,7 @@
 	$(call normalize-target-libraries,$(PRIVATE_ALL_SHARED_LIBRARIES)) \
 	-o $@ \
 	$(PRIVATE_LDFLAGS) \
+	$(PRIVATE_TARGET_LIBATOMIC) \
 	$(if $(PRIVATE_LIBCXX),,$(PRIVATE_TARGET_LIBGCC)) \
 	$(if $(filter true,$(PRIVATE_NO_CRT)),,$(PRIVATE_TARGET_CRTEND_SO_O)) \
 	$(PRIVATE_LDLIBS)
@@ -221,6 +224,7 @@
 	$(call normalize-target-libraries,$(PRIVATE_ALL_SHARED_LIBRARIES)) \
 	-o $@ \
 	$(PRIVATE_LDFLAGS) \
+	$(PRIVATE_TARGET_LIBATOMIC) \
 	$(if $(PRIVATE_LIBCXX),,$(PRIVATE_TARGET_LIBGCC)) \
 	$(if $(filter true,$(PRIVATE_NO_CRT)),,$(PRIVATE_TARGET_CRTEND_O)) \
 	$(PRIVATE_LDLIBS)
@@ -241,6 +245,7 @@
 	-Wl,--start-group \
 	$(call normalize-target-libraries,$(PRIVATE_ALL_STATIC_LIBRARIES)) \
 	$(PRIVATE_TARGET_FDO_LIB) \
+	$(PRIVATE_TARGET_LIBATOMIC) \
 	$(if $(PRIVATE_LIBCXX),,$(PRIVATE_TARGET_LIBGCC)) \
 	-Wl,--end-group \
 	$(if $(filter true,$(PRIVATE_NO_CRT)),,$(PRIVATE_TARGET_CRTEND_O))