Add F_SEAL_FUTURE_WRITE on Linux/Android

This was added in Linux 5.1 and will only show up in the next glibc
release, thus skip in tests.

Author: tklauser

libc-test/build.rs

@@ -2283,6 +2283,7 @@ fn test_linux(target: &str) {
 
             // FIXME: conflicts with glibc headers and is tested in
             // `linux_termios.rs` below:
+
             "BOTHER" => true,
 
             // FIXME: on musl the pthread types are defined a little differently
@@ -2293,6 +2294,10 @@ fn test_linux(target: &str) {
             t if mips32_musl && t.starts_with("IFF") => true,
             "MFD_HUGETLB" | "AF_XDP" | "PF_XDP" if mips32_musl => true,
 
+            // FIXME: added in Linux 5.1 but not yet in glibc or musl. Enable in linux_fcntl tests
+            // once available.
+            "F_SEAL_FUTURE_WRITE" => true,
+
             _ => false,
         }
     });

src/unix/notbsd/linux/mod.rs

@@ -1050,6 +1050,8 @@ pub const F_TEST: ::c_int = 3;
 pub const F_TLOCK: ::c_int = 2;
 pub const F_ULOCK: ::c_int = 0;
 
+pub const F_SEAL_FUTURE_WRITE: ::c_int = 0x0010;
+
 pub const IFF_LOWER_UP: ::c_int = 0x10000;
 pub const IFF_DORMANT: ::c_int = 0x20000;
 pub const IFF_ECHO: ::c_int = 0x40000;