Add getgrgid, getgrnam, getgrnam_r and getgrgid_r for emscripten

Author: ChanTsune

libc-test/semver/emscripten.txt

@@ -1,2 +1,6 @@
 getentropy
+getgrgid
+getgrnam
+getgrnam_r
+getgrgid_r
 posix_fallocate64

src/unix/linux_like/emscripten/mod.rs

@@ -1774,6 +1774,24 @@ extern "C" {
     ) -> ::c_int;
 
     pub fn getentropy(buf: *mut ::c_void, buflen: ::size_t) -> ::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