Add kbd-1.15.

This also requires a patch to linux-headers; while we are at it, make
linux-headers PREFIX agnostic.

sysa/kbd-1.15/kbd-1.15.sh

@@ -0,0 +1,30 @@
+# SPDX-FileCopyrightText: 2021 fosslinux <fosslinux@aussies.space>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+src_prepare() {
+    default
+
+    # Remove flex/bison files
+    rm src/loadkeys.c src/analyze.c
+
+    # Fix musl incompat
+    sed -i -e 's/u_char/unsigned char/g' \
+        -e 's/u_short/unsigned short/g' src/dumpkeys.c src/loadkeys.y
+
+    AUTOPOINT=true autoreconf -fi
+}
+
+src_configure() {
+    ./configure --prefix=${PREFIX}
+}
+
+src_compile() {
+    # Missing dependency in Makefile
+    flex -o src/analyze.c src/analyze.l
+    make MAKEINFO=true
+}
+
+src_install() {
+    make MAKEINFO=true DESTDIR=${DESTDIR} install
+}