Git ignore build-* instead of build-cmake.

This enables users to have several build directories like
build-clang, build-gcc5, build-debug, and still get all
of them ignored.
(cherry picked from commit a1b1f072)

.gitignore

@@ -7,7 +7,7 @@
 /aclocal.m4
 /am
 /autom4te.cache/
-/build-cmake/
+/build-*/
 /compile
 /config.guess
 /config.h
@@ -32,4 +32,4 @@
 /test-driver
 Makefile
 Makefile.in
-semantic.cache
+semantic.cache
\ No newline at end of file