libprocessgroup: remove legacy C string handling and build for host

Bug: 36970783
Test: kill zygote and see that its children die correctly
Change-Id: I1b0e9a9cdb834a000fec82323d690e3bd288692d
diff --git a/libprocessgroup/Android.bp b/libprocessgroup/Android.bp
index 1974f2c..b0bc497 100644
--- a/libprocessgroup/Android.bp
+++ b/libprocessgroup/Android.bp
@@ -1,7 +1,7 @@
 cc_library {
     srcs: ["processgroup.cpp"],
     name: "libprocessgroup",
-    defaults: ["linux_bionic_supported"],
+    host_supported: true,
     shared_libs: ["libbase"],
     export_include_dirs: ["include"],
     cflags: [