Auto merge of #2366 - electroCutie:mremap_dontunmap, r=Amanieu

Fixes #2365 by adding the MREMAP_DONTUNMAP flag

I just added the flag's value to the same file that the related flags was already in, I'm not sure where else it might need to be added for testing etc

Author: bors

libc-test/build.rs

@@ -2795,6 +2795,9 @@ fn test_linux(target: &str) {
             // Require Linux kernel 5.6:
             "VMADDR_CID_LOCAL" => true,
 
+            // Requires Linux kernel 5.7:
+            "MREMAP_DONTUNMAP" => true,
+
             // IPPROTO_MAX was increased in 5.6 for IPPROTO_MPTCP:
             | "IPPROTO_MAX"
             | "IPPROTO_MPTCP" => true,

src/unix/linux_like/linux/mod.rs

@@ -1598,6 +1598,7 @@ cfg_if! {
 
 pub const MREMAP_MAYMOVE: ::c_int = 1;
 pub const MREMAP_FIXED: ::c_int = 2;
+pub const MREMAP_DONTUNMAP: ::c_int = 4;
 
 pub const PR_SET_PDEATHSIG: ::c_int = 1;
 pub const PR_GET_PDEATHSIG: ::c_int = 2;