x86_64-musl: support the PTRACE_SYSEMU family

Author: cvengler

src/unix/linux_like/linux/musl/b64/x86_64/mod.rs

@@ -682,6 +682,9 @@ pub const O_RSYNC: ::c_int = 1052672;
 pub const O_DSYNC: ::c_int = 4096;
 pub const O_ASYNC: ::c_int = 0x2000;
 
+pub const PTRACE_SYSEMU: ::c_int = 31;
+pub const PTRACE_SYSEMU_SINGLESTEP: ::c_int = 32;
+
 pub const SIGSTKSZ: ::size_t = 8192;
 pub const MINSIGSTKSZ: ::size_t = 2048;