chore(build): parameterize deploy repositories

Adds two build parameters
- `publishing.repository.snapshots`: Snapshot repo to deploy to
- `publishing.repository.releases`: Releases repo to deploy to

Both default to their current values, Sonatype. This small inert
change allows a fork to easily publish to a different repository
without resorting to a code change.

Signed-off-by: Sam Gammon <[email protected]>
Signed-off-by: Sam Gammon <[email protected]>

pom.xml

@@ -45,6 +45,8 @@
     <otherVariant.version>1.0-HEAD-android-SNAPSHOT</otherVariant.version>
     <otherVariant.jvmEnvironment>android</otherVariant.jvmEnvironment>
     <otherVariant.jvmEnvironmentVariantName>android</otherVariant.jvmEnvironmentVariantName>
+    <publishing.repository.snapshots>https://oss.sonatype.org/content/repositories/snapshots/</publishing.repository.snapshots>
+    <publishing.repository.releases>https://oss.sonatype.org/service/local/staging/deploy/maven2/</publishing.repository.releases>
   </properties>
   <issueManagement>
     <system>GitHub Issues</system>
@@ -430,12 +432,12 @@
     <snapshotRepository>
       <id>sonatype-nexus-snapshots</id>
       <name>Sonatype Nexus Snapshots</name>
-      <url>https://oss.sonatype.org/content/repositories/snapshots/</url>
+      <url>${publishing.repository.snapshots}</url>
     </snapshotRepository>
     <repository>
       <id>sonatype-nexus-staging</id>
       <name>Nexus Release Repository</name>
-      <url>https://oss.sonatype.org/service/local/staging/deploy/maven2/</url>
+      <url>${publishing.repository.releases}</url>
     </repository>
     <site>
       <id>guava-site</id>