riot: fix gradle out of memory errors

Work around weird versioning scheme for now.

metadata/im.vector.alpha.yml

@@ -1860,6 +1860,7 @@ Builds:
     prebuild:
       - sed -i -e '/com.google.firebase/,+5d' build.gradle
       - sed -i -e '/com.google.gms.google-services/d' build.gradle
+      - echo "org.gradle.jvmargs=-Xmx4g" >> ../gradle.properties
     scanignore:
       - build.gradle
 
@@ -1886,6 +1887,7 @@ Builds:
     prebuild:
       - sed -i -e '/com.google.firebase/,+5d' build.gradle
       - sed -i -e '/com.google.gms.google-services/d' build.gradle
+      - echo "org.gradle.jvmargs=-Xmx4g" >> ../gradle.properties
     scanignore:
       - build.gradle
 
@@ -1912,6 +1914,7 @@ Builds:
     prebuild:
       - sed -i -e '/com.google.firebase/,+5d' build.gradle
       - sed -i -e '/com.google.gms.google-services/d' build.gradle
+      - echo "org.gradle.jvmargs=-Xmx4g" >> ../gradle.properties
     scanignore:
       - build.gradle
 
@@ -1938,13 +1941,14 @@ Builds:
     prebuild:
       - sed -i -e '/com.google.firebase/,+5d' build.gradle
       - sed -i -e '/com.google.gms.google-services/d' build.gradle
+      - echo "org.gradle.jvmargs=-Xmx4g" >> ../gradle.properties
     scanignore:
       - build.gradle
 
 MaintainerNotes: Upstream builds and publishes a libre build of the jitsi sdk. The
     sdk build and riot use that sdk. The maven repo can be re=created by using ./build_jitsi_libs.sh
 
-ArchivePolicy: 6 versions
+ArchivePolicy: 10 versions
 AutoUpdateMode: None
 UpdateCheckMode: Tags
 CurrentVersion: 0.9.8