ci: build: remove duplicate CI_BUILD_PROFILE export from script section

The CI_BUILD_PROFILE variable was being set twice:
1. In before_script (for all jobs)
2. In the script section during gen-config (redundant)

This duplication caused issues when jobs needed to override the variable
extraction pattern (e.g., blackduck scan jobs use a different job name
pattern than build test jobs).

Since before_script runs before script and the variable persists across
both sections, the second export in the script section is unnecessary
and was overwriting custom values set by derived jobs.

This change removes the redundant export from the script section,
allowing jobs that extend .build test config to properly override
CI_BUILD_PROFILE in their before_script without it being overwritten.

No functional change for existing build test jobs.

References: PPW-1194

Signed-off-by: Mouna Aloui <mouna.aloui@softathome.com>

.gitlab/build.yml

@@ -53,7 +53,6 @@
     - section_start "gen-config" "Running gen_config.py" "collapsed"
     - |
       sed -i -E 's;git.openwrt.org/(feed|project);github.com/openwrt;' feeds.conf.default
-      export CI_BUILD_PROFILE="$(echo $CI_JOB_NAME | sed 's/build test \(.*\)/\1/')"
       scripts/gen_config.py $CI_BUILD_PROFILE 2>&1 | tee logs/build.log
       git checkout -- feeds.conf.default
     - section_end "gen-config"