Add getgrgid, getgrnam, getgrnam_r and getgrgid_r for emscrip…

…ten (rust-lang#3912)

(backport <rust-lang#3912>)
(cherry picked from commit 1566923)

libc-test/semver/emscripten.txt

@@ -1,5 +1,9 @@
 AT_EACCESS
 getentropy
+getgrgid
+getgrnam
+getgrnam_r
+getgrgid_r
 posix_fallocate64
 getpwnam_r
 getpwuid_r

src/unix/linux_like/emscripten/mod.rs

@@ -1793,6 +1793,24 @@ extern "C" {
         buflen: ::size_t,
         result: *mut *mut passwd,
     ) -> ::c_int;
+
+    // grp.h
+    pub fn getgrgid(gid: ::gid_t) -> *mut ::group;
+    pub fn getgrnam(name: *const ::c_char) -> *mut ::group;
+    pub fn getgrnam_r(
+        name: *const ::c_char,
+        grp: *mut ::group,
+        buf: *mut ::c_char,
+        buflen: ::size_t,
+        result: *mut *mut ::group,
+    ) -> ::c_int;
+    pub fn getgrgid_r(
+        gid: ::gid_t,
+        grp: *mut ::group,
+        buf: *mut ::c_char,
+        buflen: ::size_t,
+        result: *mut *mut ::group,
+    ) -> ::c_int;
 }
 
 // Alias <foo> to <foo>64 to mimic glibc's LFS64 support