Toolchain: Oops, we can't rely on "install.sh" to build LibC/LibM.

When we used "make install" in the past, the "install" target would pull
in the library targets as dependencies, and everything got built that way.
Now that we use "install.sh" instead, we have to build things manually.

Toolchain/BuildIt.sh

@@ -93,8 +93,8 @@ pushd "$DIR/Build/"
         make install-gcc install-target-libgcc || exit 1
 
         echo "XXX serenity libc and libm"
-        ( cd "$DIR/../Libraries/LibC/" && ./install.sh )
-        ( cd "$DIR/../Libraries/LibM/" && ./install.sh )
+        ( cd "$DIR/../Libraries/LibC/" && make clean && make && ./install.sh )
+        ( cd "$DIR/../Libraries/LibM/" && make clean && make && ./install.sh )
 
         echo "XXX build libstdc++"
         make all-target-libstdc++-v3 || exit 1