fetch SBCL from github

As mentioned in #8, SBCL also hosts its source code on github,
which is more reliable and faster than sourceforge

It does not include binaries for bootstrapping, so we temporarily
install debian's sbcl version

buildscript.sh

@@ -15,16 +15,18 @@ apt-get update
 apt-get install -y bzip2 make wget python3 gcc texinfo curl libcap2-bin
 
 mkdir -p ${SRC}
-wget https://sourceforge.net/projects/maxima/files/Maxima-source/${MAXIMA_VERSION}-source/maxima-${MAXIMA_VERSION}.tar.gz -O ${SRC}/maxima-${MAXIMA_VERSION}.tar.gz
-wget https://sourceforge.net/projects/sbcl/files/sbcl/${SBCL_VERSION}/sbcl-${SBCL_VERSION}-${SBCL_ARCH}-linux-binary.tar.bz2 -O ${SRC}/sbcl-${SBCL_VERSION}-${SBCL_ARCH}-linux.tar.bz2
+wget "https://sourceforge.net/projects/maxima/files/Maxima-source/${MAXIMA_VERSION}-source/maxima-${MAXIMA_VERSION}.tar.gz" -O "${SRC}/maxima-${MAXIMA_VERSION}.tar.gz"
+wget "https://github.com/sbcl/sbcl/archive/refs/tags/sbcl-${SBCL_VERSION}.tar.gz" -O "${SRC}/sbcl-${SBCL_VERSION}.tar.gz"
 
-# Compile sbcl
+# Compile sbcl (installs and removes debian sbcl for bootstrapping)
+apt install -y sbcl
 cd ${SRC}
-bzip2 -d sbcl-${SBCL_VERSION}-${SBCL_ARCH}-linux.tar.bz2
-tar -xf sbcl-${SBCL_VERSION}-${SBCL_ARCH}-linux.tar
-rm sbcl-${SBCL_VERSION}-${SBCL_ARCH}-linux.tar
-ls
-cd sbcl-${SBCL_VERSION}-${SBCL_ARCH}-linux
+tar -xzf sbcl-${SBCL_VERSION}.tar.gz
+rm sbcl-${SBCL_VERSION}.tar.gz
+cd sbcl-sbcl-${SBCL_VERSION}
+echo "\"$SBCL_VERSION\"" > version.lisp-expr
+./make.sh
+apt remove -y sbcl
 ./install.sh
 
 # Compile maxima