Refactor post_process_props.py

The script is refactored to not parse lines everytime a prop is looked
up or updated.

Also it is now built using python_binary_host.

Bug: 117892318
Test: m

Change-Id: I1677ca5aa919c54b7b0740fdc52e1399009f9a12
diff --git a/core/sysprop.mk b/core/sysprop.mk
index d3712da..e2a3153 100644
--- a/core/sysprop.mk
+++ b/core/sysprop.mk
@@ -25,7 +25,7 @@
 
 BUILDINFO_SH := build/make/tools/buildinfo.sh
 BUILDINFO_COMMON_SH := build/make/tools/buildinfo_common.sh
-POST_PROCESS_PROPS :=$= build/make/tools/post_process_props.py
+POST_PROCESS_PROPS := $(HOST_OUT_EXECUTABLES)/post_process_props$(HOST_EXECUTABLE_SUFFIX)
 
 # Generates a set of sysprops common to all partitions to a file.
 # $(1): Partition name