Disable building btls/ and support/ on the bcl build, they are not needed.

sdks/builds/bcl.mk

@@ -15,6 +15,8 @@ bcl_CONFIGURE_FLAGS = \
        $(if $(DISABLE_WASM),,--with-wasm=yes) \
        --with-mcs-docs=no \
        --disable-nls \
+       --disable-btls-lib \
+       --disable-support-build \
        --disable-boehm
 
 .stamp-bcl-configure: $(TOP)/configure