tools lib api: Add str_error_c to libapi

Because it uses that function, which would lead every tool using it
to need to link against tools/lib/str_error_r.o.

This fixes building tools/vm/, that links with libapi.

Reported-by: Arjan van de Ven <[e-mail]>
Reported-by: Randy Dunlap <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Wang Nan <[e-mail]>
Fixes: b31e3e3316a7 ("tools lib api fs: Use str_error_r()")
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/lib/api/Build

···
 libapi-y += fs/
 libapi-y += cpu.o
 libapi-y += debug.o
+libapi-y += str_error_r.o
+
+$(OUTPUT)str_error_r.o: ../str_error_r.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cc_o_c)

tools/perf/util/Build

···
 libperf-y += stat-shadow.o
 libperf-y += record.o
 libperf-y += srcline.o
-libperf-y += str_error_r.o
 libperf-y += data.o
 libperf-y += tsc.o
 libperf-y += cloexec.o
···
 	$(call if_changed_dep,cc_o_c)
 
 $(OUTPUT)util/libstring.o: ../lib/string.c FORCE
-	$(call rule_mkdir)
-	$(call if_changed_dep,cc_o_c)
-
-$(OUTPUT)util/str_error_r.o: ../lib/str_error_r.c FORCE
 	$(call rule_mkdir)
 	$(call if_changed_dep,cc_o_c)
 

tools/perf/util/python-ext-sources

···
 ../lib/bitmap.c
 ../lib/find_bit.c
 ../lib/hweight.c
-../lib/str_error_r.c
 ../lib/vsprintf.c
 util/thread_map.c
 util/util.c