Add cgo support

[szkiba]

Certain extensions require cgo to be enabled. For these extensions to work correctly, cgo support must be implemented (setting the CGO_ENABLED=1 environment variable during build).

Background

The k6 extension registry/catalog includes a cgo boolean property for extensions. A true value indicates that cgo is required to compile the extension.

The sqlite3 diver of the grafana/xk6-sql extension, grafana/xk6-sql-driver-sqlite3, for example, requires cgo to be enabled.
https://registry.k6.io/module/github.com%2Fgrafana%2Fxk6-sql-driver-sqlite3/extension.json

[szkiba]

@pablochacin , as you requested in issue #5, I opened a new issue about cgo support. Since xk6-sql is a popular extension and can be tested most easily with the sqlite3 driver, it would be important to implement cgo support for the start of binary provisioning.

[pablochacin]

@szkiba appreciated. This is much more clear and actionable. Thanks.