BUILD: Makefile: add "USE_SHM_OPEN" on the linux-musl target

The startup-logs with the shm works correctly with Alpine and Musl,
enable the feature by default for the linux-musl target.
diff --git a/Makefile b/Makefile
index 9123e02..8e70ab7 100644
--- a/Makefile
+++ b/Makefile
@@ -403,7 +403,7 @@
     USE_POLL USE_TPROXY USE_LIBCRYPT USE_DL USE_RT USE_CRYPT_H USE_NETFILTER  \
     USE_CPU_AFFINITY USE_THREAD USE_EPOLL USE_LINUX_TPROXY                    \
     USE_ACCEPT4 USE_LINUX_SPLICE USE_PRCTL USE_THREAD_DUMP USE_NS USE_TFO     \
-    USE_GETADDRINFO)
+    USE_GETADDRINFO USE_SHM_OPEN)
   INSTALL = install -v
 endif