build-all: Stop requiring curl to be available

Curl (or wget) isn't required for fetching libssp any longer,
so don't require it while running build-all.sh.

(It's still required by build-cross-tools.sh, for build-make.sh
though.)

Dockerfile.dev

@@ -153,10 +153,6 @@ RUN cd test && \
         done; \
     done
 
-# Build libssp
-COPY build-libssp.sh ./
-RUN ./build-libssp.sh $TOOLCHAIN_PREFIX
-
 RUN cd test && \
     for arch in $TOOLCHAIN_ARCHS; do \
         mkdir -p $arch && \