Build both stages of curl in sysc

The source tarball is provided as part of sysa distfiles and copied to sysc, which resolves the issue of finding a reliable plain HTTP mirror for curl.

Splitted from https://github.com/fosslinux/live-bootstrap/pull/253.

sysc/curl-7.88.1/pass2.sh

@@ -0,0 +1,29 @@
+# SPDX-FileCopyrightText: 2022 fosslinux <fosslinux@aussies.space>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+src_prepare() {
+    default
+
+    # Regnerate src/tool_cb_prg.c
+    sed -i "55,76d" src/tool_cb_prg.c
+    sed -i "55 s/^/$(perl sinus.pl | sed "s/, $//")\n/" src/tool_cb_prg.c
+
+    rm src/tool_help.c src/tool_help.h src/tool_listhelp.c src/tool_hugehelp.c
+
+    # Rebuild libtool files
+    rm config.guess config.sub ltmain.sh
+    libtoolize
+
+    AUTOMAKE=automake-1.15 ACLOCAL=aclocal-1.15 autoreconf-2.69 -fi
+}
+
+src_configure() {
+    LDFLAGS="-static" ./configure \
+        --prefix="${PREFIX}" \
+        --libdir="${LIBDIR}" \
+        --build=i386-unknown-linux-musl \
+        --enable-ipv6 \
+        --with-openssl \
+        --with-ca-bundle=/etc/ssl/certs.pem
+}