Add AT_EACCESS to emscripten (#3911)

https://github.com/emscripten-core/emscripten/blob/3073806d3fde4320c81cb2dc7cf0e00378f52df1/system/lib/libc/musl/include/fcntl.h#L68

Author: ChanTsune

libc-test/semver/emscripten.txt

@@ -1,3 +1,4 @@
+AT_EACCESS
 getentropy
 posix_fallocate64
 getpwnam_r

src/unix/linux_like/emscripten/mod.rs

@@ -775,6 +775,8 @@ pub const POSIX_MADV_RANDOM: ::c_int = 1;
 pub const POSIX_MADV_SEQUENTIAL: ::c_int = 2;
 pub const POSIX_MADV_WILLNEED: ::c_int = 3;
 
+pub const AT_EACCESS: ::c_int = 0x200;
+
 pub const S_IEXEC: mode_t = 0o0100;
 pub const S_IWRITE: mode_t = 0o0200;
 pub const S_IREAD: mode_t = 0o0400;