perf build: Do not fail on missing Build file

Allow nesting into directories without Build file. Currently we force
include of the Build file, which fails the build when the Build file is
missing.

We already support empty *-in.o' objects if there's nothing in the
directory to be compiled, so we can just use it for missing Build file
cases.

Also adding this case under tests.

Reported-by: Rabin Vincent <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rabin Vincent <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

3 files changed, 4 insertions, 1 deletions

diff --git a/tools/build/Makefile.build b/tools/build/Makefile.build
index 10df57237a66..69c35cf09cad 100644
--- a/tools/build/Makefile.build
+++ b/tools/build/Makefile.build
@@ -37,7 +37,7 @@ subdir-obj-y :=
 
 # Build definitions
 build-file := $(dir)/Build
-include $(build-file)
+-include $(build-file)
 
 quiet_cmd_flex  = FLEX     $@
 quiet_cmd_bison = BISON    $@
diff --git a/tools/build/tests/ex/Build b/tools/build/tests/ex/Build
index 0e6c3e6767e6..70d876237c57 100644
--- a/tools/build/tests/ex/Build
+++ b/tools/build/tests/ex/Build
@@ -2,6 +2,7 @@ ex-y += ex.o
 ex-y += a.o
 ex-y += b.o
 ex-y += empty/
+ex-y += empty2/
 
 libex-y += c.o
 libex-y += d.o
diff --git a/tools/build/tests/ex/empty2/README b/tools/build/tests/ex/empty2/README
new file mode 100644
index 000000000000..2107cc5bf5a9
--- /dev/null
+++ b/tools/build/tests/ex/empty2/README
@@ -0,0 +1,2 @@
+This directory is left intentionally without Build file
+to test proper nesting into Build-less directories.