Readd posix_spawn{_file_actions_t,attr_t} on Android

Fixes: rust-lang#3709
Fixes: rust-lang#3608
Fixes: rust-lang#3677

Co-authored-by: Jorge Aparicio <jorge.aparicio@ferrous-systems.com>

[resolved conflict, update commit message - Trevor]
(apply <rust-lang#3690> to `main`)
(cherry picked from commit b2b2fd7)

Signed-off-by: Trevor Gross <tmgross@umich.edu>

libc-test/build.rs

@@ -1550,6 +1550,7 @@ fn test_android(target: &str) {
                "sched.h",
                "semaphore.h",
                "signal.h",
+               "spawn.h",
                "stddef.h",
                "stdint.h",
                "stdio.h",
@@ -1709,6 +1710,10 @@ fn test_android(target: &str) {
 
             // FIXME: Somehow fails to test after removing cfg hacks:
             "__uint128" => true,
+
+            // These are intended to be opaque
+            "posix_spawn_file_actions_t" => true,
+            "posix_spawnattr_t" => true,
             _ => false,
         }
     });

src/unix/linux_like/android/mod.rs

@@ -48,6 +48,10 @@ pub type Elf64_Xword = u64;
 
 pub type eventfd_t = u64;
 
+// these structs sit behind a heap allocation on Android
+pub type posix_spawn_file_actions_t = *mut ::c_void;
+pub type posix_spawnattr_t = *mut ::c_void;
+
 s! {
     pub struct stack_t {
         pub ss_sp: *mut ::c_void,