(First of all thank you for the great build tool!)

Go 1.24 introduced new #cgo directives for performance improvements. Unfortunately the current pants go plugin does not understand the directives and results in the following error when building:

21:02:21.05 [ERROR] Failed to analyze github.com/pantsbuild/pants/testprojects/src/go/pants_test/cgo/directives for dependency inference:
invalid Go sources encountered
nocallback_noescape.go: cgo error: nocallback_noescape.go: invalid #cgo line: #cgo nocallback addNumbers

The error message was obtained by running the new test ./pants test testprojects/src/go/pants_test/cgo/directives: with the following diff (to recognize code under testprojects/src/go/).

diff --git a/pants.toml b/pants.toml
index fde22eaf8e..f3e4f56313 100644
--- a/pants.toml
+++ b/pants.toml
@@ -72,7 +72,7 @@ pants_ignore.add = [

 build_ignore.add = [
   # Disable Go targets by default so Pants developers do not need Go installed.
-  "testprojects/src/go/**",
+  # "testprojects/src/go/**",
 ]

 unmatched_build_file_globs = "error"

This PR fixes the issue by changing saveCgo function in go package analyzer. Specifically I updated saveCgo based on https://github.com/golang/go/blob/go1.26.4/src/go/build/build.go#L1710-L1713 (i.e. catch up with upstream) so that #cgo nocallback directive is not rejected.

I also added a simple cgo test case. Please let me know if you have a better idea how to test this feature.