update amalgamation code

fix syntax error

fix test

Update amalgamation code to 3.50.3

upgrade amalgamation code

revert #1259

docs: clarify GCP section

GCP (at least Google Compute Engine) is a VM, and does not have restrictions relating to gcc.

Also it appears that this whole section refers to general compiling, rather than compiling on GCP.

Update amalgamation code to 3.46.1

Update amalgamation code to 3.46.1

chore: Fix memory leak in callbackRetText function