Move to /usr prefix.

- This is much more standard and replaces /image in sysa and is the
  standard in sysc (avoids many issues).
- GCC needs to have a file created for some unknown reason.
- Checksums updated.

sysc/patch-2.7.6/patch-2.7.6.sh

@@ -0,0 +1,24 @@
+# SPDX-FileCopyrightText: 2021 Andrius Štikonas <andrius@stikonas.eu>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+src_prepare() {
+    ../../import-gnulib.sh
+
+    # bison
+    rm lib/parse-datetime.c
+
+    autoreconf -fi
+}
+
+src_configure() {
+    ./configure --prefix="${PREFIX}"
+}
+
+src_compile() {
+    make MAKEINFO=true
+}
+
+src_install() {
+    make MAKEINFO=true DESTDIR="${DESTDIR}" install
+}