Rework how linux_bionic is built with LLD

In order to simplify the wrapper function, and stop using a linker
script, generate a set of flags to pass to LLD. Then run
host_bionic_inject on the linked binary in order to verify the
embedding, and give the wrapper function the address of the original
entry point (_start).

Bug: 31559095
Test: build host bionic with prebuilts/build-tools/build-prebuilts.sh
Change-Id: I53e326050e0f9caa562c6cf6f76c4d0337bb6faf
diff --git a/Android.bp b/Android.bp
index bdc34d0..bcf831d 100644
--- a/Android.bp
+++ b/Android.bp
@@ -482,7 +482,7 @@
 }
 
 cc_genrule {
-    name: "host_bionic_linker_script",
+    name: "host_bionic_linker_flags",
     host_supported: true,
     device_supported: false,
     target: {
@@ -497,7 +497,7 @@
         },
     },
     tools: ["extract_linker"],
-    cmd: "$(location) -T $(out) $(in)",
+    cmd: "$(location) -f $(out) $(in)",
     srcs: [":linker"],
-    out: ["linker.script"],
+    out: ["linker.flags"],
 }