libatomic build failure if configured with --disable-dependency-tracking
load_n.c:115:1: fatal error: opening dependency file .deps/load_1_.lo.Ppo: No such file or directory

https://bugs.gentoo.org/463463
http://gcc.gnu.org/PR55930

--- a/libatomic/Makefile.in
+++ b/libatomic/Makefile.in
@@ -298,7 +298,8 @@ PAT_N = $(word 2,$(PAT_SPLIT))
 PAT_S = $(word 3,$(PAT_SPLIT))
 IFUNC_DEF = -DIFUNC_ALT=$(PAT_S)
 IFUNC_OPT = $(word $(PAT_S),$(IFUNC_OPTIONS))
-M_DEPS = -MT $@ -MD -MP -MF $(DEPDIR)/$(@F).Ppo
+@AMDEP_TRUE@M_DEPS = -MT $@ -MD -MP -MF $(DEPDIR)/$(@F).Ppo
+@AMDEP_FALSE@M_DEPS =
 M_SIZE = -DN=$(PAT_N)
 M_IFUNC = $(if $(PAT_S),$(IFUNC_DEF) $(IFUNC_OPT))
 M_FILE = $(PAT_BASE)_n.c