galileo: Fix bug in newlib build script

This patch fixes a bug in the newlib build script that causes it to
not delete an old source directory as intended prior to rebuilding the
library.

platform/galileo/bsp/libc/build_newlib.sh

@@ -31,8 +31,8 @@ prepare() {
     fi
 
     # Clean up the previous install dir, if any.
-    if [[ -d ./${VERSION} ]]; then
-        rm -rf ./${VERSION}
+    if [[ -d ./${TARGET} ]]; then
+        rm -rf ./${TARGET}
     fi
 
     tar xf ${TARBALL}