Use libwhatever.a naming for static libraries on mingw, as that matches

how all libraries shipped with mingw are named. Further, we previously
used libwhatever.lib, and the linker never searched for this spelling.


[SVN r57816]

tools/build

@@ -1 +1 @@
-Subproject commit 10c496d79cd78126272041e6bed03be394767217
+Subproject commit a52d4903a90a3049d387d5d38594eae00bad48ee