RFR: JDK-8189376 Unsorted $(wildcard) causes instable module-deps.gmk

[Magnus Ihse Bursie]

We have implicitly assumed that subsequent calls to $(wildcard) will 
return the same (sorted) order of files during a single build operation. 
This is not guaranteed since GNU make 3.82, but will be the case in 
practice on most systems due the the filesystem being used.

It turned out that if the order was different, FindAllModuleInfos 
returned different strings which in turn caused module-deps.gmk to be 
re-generated at any time during the build, causing race conditions.

The bug analysis and patch is contributed by Martin Buchholz.

Bug: https://bugs.openjdk.java.net/browse/JDK-8189376
Patch inline:
diff --git a/make/common/Modules.gmk b/make/common/Modules.gmk
--- a/make/common/Modules.gmk
+++ b/make/common/Modules.gmk
@@ -249,10 +249,10 @@
  # configuration.
  # Param 1 - Module to find for, set to * for finding all
  FindAllModuleInfos = \
-    $(wildcard \
+    $(sort $(wildcard \
          $(foreach sub, $(SRC_SUBDIRS), \
            $(patsubst %,%/$(strip $1)/$(sub)/module-info.java, 
$(TOP_SRC_DIRS))) \
-        $(patsubst %,%/$(strip $1)/module-info.java, 
$(IMPORT_MODULES_SRC)))
+        $(patsubst %,%/$(strip $1)/module-info.java, 
$(IMPORT_MODULES_SRC))))

  # Find module-info.java files in the specific source dir
  # Param 1 - Src dir to find module-info.java files in

/Magnus