doc: Update broken links to now point to gitian-build.py

Author: MitchellCash

contrib/README.md

@@ -37,7 +37,7 @@ Scripts and notes for Mac builds.
 ### [RPM](/contrib/rpm) ###
 RPM spec file for building bitcoin-core on RPM based distributions.
 
-### [Gitian-build](/contrib/gitian-build.sh) ###
+### [Gitian-build](/contrib/gitian-build.py) ###
 Script for running full Gitian builds.
 
 Test and Verify Tools 

doc/release-process.md

@@ -29,7 +29,7 @@ Before every major release:
 
 ### First time / New builders
 
-If you're using the automated script (found in [contrib/gitian-build.sh](/contrib/gitian-build.sh)), then at this point you should run it with the "--setup" command. Otherwise ignore this.
+If you're using the automated script (found in [contrib/gitian-build.py](/contrib/gitian-build.py)), then at this point you should run it with the "--setup" command. Otherwise ignore this.
 
 Check out the source code in the following directory hierarchy.
 
@@ -58,7 +58,7 @@ Tag version (or release candidate) in git
 
 ### Setup and perform Gitian builds
 
-If you're using the automated script (found in [contrib/gitian-build.sh](/contrib/gitian-build.sh)), then at this point you should run it with the "--build" command. Otherwise ignore this.
+If you're using the automated script (found in [contrib/gitian-build.py](/contrib/gitian-build.py)), then at this point you should run it with the "--build" command. Otherwise ignore this.
 
 Setup Gitian descriptors: