Replace killpg.

Upstream's killpg is diverging further from glibc behavior, so let's just fork.

Bug: N/A
Test: ran tests
Change-Id: I70a3543018bc0a5c0bbf019ac527043b90568fda
diff --git a/libc/Android.bp b/libc/Android.bp
index cd2a727..ccb831c 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -385,7 +385,6 @@
     name: "libc_openbsd_ndk",
     defaults: ["libc_defaults"],
     srcs: [
-        "upstream-openbsd/lib/libc/compat-43/killpg.c",
         "upstream-openbsd/lib/libc/gen/alarm.c",
         "upstream-openbsd/lib/libc/gen/ctype_.c",
         "upstream-openbsd/lib/libc/gen/daemon.c",
@@ -1392,6 +1391,7 @@
         "bionic/ifaddrs.cpp",
         "bionic/inotify_init.cpp",
         "bionic/ioctl.cpp",
+        "bionic/killpg.cpp",
         "bionic/langinfo.cpp",
         "bionic/lchown.cpp",
         "bionic/lfs64_support.cpp",