sys-apps/systemd: add v256.5 with musl libc patches

- https://code.atwilcox.tech/sphen/scaly/systemd
- https://catfox.life/2024/09/05/porting-systemd-to-musl-libc-powered-linux/

sys-apps/systemd/files/0015-basic-Define-our-own-basename.patch

@@ -0,0 +1,34 @@
+From 6ef506dbf1d28618d92f0b9bb2b2fa2b989acd99 Mon Sep 17 00:00:00 2001
+From: "A. Wilcox" <AWilcox@Wilcox-Tech.com>
+Date: Sun, 18 Aug 2024 02:50:50 -0500
+Subject: [PATCH 15/34] basic: Define our own basename
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 8bit
+
+This prevents issues where the POSIX basename is not the same as the GNU
+basename.  I think maybe upstream could be convinced since glibc does
+provide the POSIX one as well, but until then, let's do this.
+
+This cannot be upstreamed.
+
+Signed-off-by: Alexander Miroshnichenko <alex@millerson.name>
+---
+ src/basic/string-util.h | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/src/basic/string-util.h b/src/basic/string-util.h
+index ff5efbcf557b..656f5100e202 100644
+--- a/src/basic/string-util.h
++++ b/src/basic/string-util.h
+@@ -26,6 +26,8 @@
+ #define URI_UNRESERVED      ALPHANUMERICAL "-._~"       /* [RFC3986] */
+ #define URI_VALID           URI_RESERVED URI_UNRESERVED /* [RFC3986] */
+ 
++#define basename(src) (strrchr(src,'/') ? strrchr(src,'/')+1 : src)
++
+ static inline char* strstr_ptr(const char *haystack, const char *needle) {
+         if (!haystack || !needle)
+                 return NULL;
+-- 
+2.41.0
+