Re-make showmap host supported

Also fix bugs that made it not compile on host. Motivation is to be
able to analyze smaps files easily on the host.

Test: showmap -f maps.txt
Bug: 137034556

Change-Id: I7b8ca1237ce1ec17d02cd5217c73b62ee978cb05
diff --git a/libmeminfo/tools/Android.bp b/libmeminfo/tools/Android.bp
index 2e89c41..a592a25 100644
--- a/libmeminfo/tools/Android.bp
+++ b/libmeminfo/tools/Android.bp
@@ -56,6 +56,7 @@
 
 cc_binary {
     name: "showmap",
+    host_supported: true,
     cflags: [
         "-Wall",
         "-Werror",