Fix CRLF breakage in Linux build scripts

The Linux build host reads these scripts from a shared mount of the
Windows working tree, where autocrlf produces CRLF line endings. bash
then failed on `set -o pipefail` (trailing CR in the option name), and
the version parsed from version.go carried a trailing CR into the Docker
tag ("...:0.6.0\r": invalid reference format).

- Add .gitattributes forcing LF on *.sh so Windows checkouts stay LF.
- Strip CR from the version extraction in all three Linux build scripts.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,3 @@
+# Keep shell scripts LF even on Windows checkouts so bash on Linux hosts
+# doesn't choke on trailing CRs (e.g. "set: pipefail: invalid parameter name").
+*.sh text eol=lf