fix bug #51076 (race condition in shtool's mkdir -p)

NEWS

@@ -2,6 +2,10 @@ PHP                                                                        NEWS
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 ?? ??? 2013, PHP 5.5.5
 
+- Buildsystem:
+  . Fixed bug #51076 (race condition in shtool's mkdir -p implementation).
+    (Mike, Raphael Geissert)
+
 - Core:
   . Fixed bug #64979 (Wrong behavior of static variables in closure generators).
     (Nikita)

build/shtool

@@ -1003,7 +1003,14 @@ mkdir )
                     if [ ".$opt_t" = .yes ]; then
                         echo "mkdir $pathcomp" 1>&2
                     fi
-                    mkdir $pathcomp || errstatus=$?
+					# See https://bugs.php.net/51076
+					# The fix is from Debian who have sent it
+					# upstream, too; but upstream seems dead.
+                    mkdir $pathcomp || {
+                        _errstatus=$?
+                        [ -d "$pathcomp" ] || errstatus=${_errstatus}
+                        unset _errstatus
+                    }
                     if [ ".$opt_o" != . ]; then
                         if [ ".$opt_t" = .yes ]; then
                             echo "chown $opt_o $pathcomp" 1>&2