Fix CI for FreeBSD 15 (#3950)

It was failing for two reasons:

* 87fbd9fc7[^1] removed the TCP_MAXPEAKRATE symbol.
* 3458bbd39[^2] changed the value of RLIM_NLIMITS

Fixes #3947

[^1]: freebsd/freebsd-src@87fbd9f
[^2]: freebsd/freebsd-src@3458bbd

libc-test/build.rs

@@ -2306,6 +2306,10 @@ fn test_freebsd(target: &str) {
  | "PWAIT" | "PLOCK" | "PPAUSE" | "PRI_MIN_TIMESHARE" | "PUSER" | "PI_AV" | "PI_NET"
  | "PI_DISK" | "PI_TTY" | "PI_DULL" | "PI_SOFT" => true,
 
+ // This constant changed in FreeBSD 15 (git 3458bbd397783). It was never intended to
+ // be stable, and probably shouldn't be bound by libc at all.
+ "RLIM_NLIMITS" => true,
+
  // This symbol changed in FreeBSD 14 (git 051e7d78b03), but the new
  // version should be safe to use on older releases.
  "IFCAP_CANTCHANGE" => true,
@@ -2436,7 +2440,6 @@ fn test_freebsd(target: &str) {
 
  // Flags introduced in FreeBSD 14.
  "TCP_MAXUNACKTIME"
- | "TCP_MAXPEAKRATE"
  | "TCP_IDLE_REDUCE"
  | "TCP_REMOTE_UDP_ENCAPS_PORT"
  | "TCP_DELACK"

libc-test/semver/freebsd.txt

@@ -1494,7 +1494,6 @@ TCP_KEEPIDLE
 TCP_KEEPINIT
 TCP_KEEPINTVL
 TCP_LOG_LIMIT
-TCP_MAXPEAKRATE
 TCP_MAXSEG
 TCP_MAXUNACKTIME
 TCP_MD5SIG

src/unix/bsd/freebsdlike/freebsd/mod.rs

@@ -3779,7 +3779,6 @@ pub const TCP_INFO: ::c_int = 32;
 pub const TCP_CONGESTION: ::c_int = 64;
 pub const TCP_CCALGOOPT: ::c_int = 65;
 pub const TCP_MAXUNACKTIME: ::c_int = 68;
-pub const TCP_MAXPEAKRATE: ::c_int = 69;
 pub const TCP_IDLE_REDUCE: ::c_int = 70;
 pub const TCP_REMOTE_UDP_ENCAPS_PORT: ::c_int = 71;
 pub const TCP_DELACK: ::c_int = 72;