Enable all webpack sourcemaps in dev build, disable all in prod build (#25089)

- Enable all source maps in dev build
- Disable all source maps in prod build
- Provide `ENABLE_SOURCEMAP` env var to override it.

I think the strange error seen in
https://github.com/go-gitea/gitea/issues/24784 is sourcemap related, so
if we enable/disable them all, it might go away. But it's most
definitely a Safari bug.

With all sourcemaps disabled, binary size goes down by around 1-2 MB,
with all enabled it goes up by around 12MB. If +12MB is acceptable, we
could also always enable them by default as fully source maps do have
some debugging benefits.

1 files changed, 2 insertions, 0 deletions

diff --git a/docs/content/doc/installation/from-source.en-us.md b/docs/content/doc/installation/from-source.en-us.md
index e0be7f2f14..dfded3d9fd 100644
--- a/docs/content/doc/installation/from-source.en-us.md
+++ b/docs/content/doc/installation/from-source.en-us.md
@@ -132,6 +132,8 @@ If pre-built frontend files are present it is possible to only build the backend
 TAGS="bindata" make backend
 ```
 
+Webpack source maps are by default enabled in development builds and disabled in production builds. They can be enabled by setting the `ENABLE_SOURCEMAP=true` environment variable.
+
 ## Test
 
 After following the steps above, a `gitea` binary will be available in the working directory.