Strip PHP binary and create runtime layer w/ "zip -9"

See https://stackoverflow.com/questions/4179010/how-to-strip-executables-thoroughly

Author: thekid

ChangeLog.md

@@ -3,6 +3,10 @@ AWS Lambda change log
 
 ## ?.?.? / ????-??-??
 
+* Decreased size of runtime layer from ~8.4 MB to ~2.4 MB by using `strip`
+  and `zip -9`, reducing layer publishing time as well as initialization duration
+  https://stackoverflow.com/questions/4179010/how-to-strip-executables-thoroughly
+
 ## 0.5.0 / 2021-08-22
 
 * Renamed `task.zip` to `function.zip` in order not to introduce more

src/main/php/xp/lambda/Dockerfile.runtime

@@ -38,4 +38,4 @@ RUN curl -L https://baltocdn.com/xp-framework/xp-runners/distribution/downloads/
   | sed -e 's/"$@"/xp.lambda.AwsRunner/g' > /opt/php/bootstrap \
   && chmod 755 /opt/php/bootstrap
 
-RUN cd /opt/php && zip runtime.zip bin/php bootstrap
+RUN cd /opt/php && strip bin/php && zip -9 runtime.zip bin/php bootstrap