etc/Build.sh: drop dead isNinja block to fix unbound variable

The isNinja branch was never reachable (no code path sets it) and under
'set -euo pipefail' it terminated the script with 'isNinja: unbound
variable' at line 358 once master's removal of the ninja option (commit
4e494df) was merged in. Remove the dead block.

Reported by maliberty in #9762.

Signed-off-by: alokkumardalei-wq <alokkumardalei2@gmail.com>

Author: alokkumardalei-wq

etc/Build.sh

@@ -355,11 +355,5 @@ if [[ "$useBazel" == "yes" ]]; then
     "${bazel_cmd}" build "${bazelArgs[@]}" //:openroad
     exit 0
 fi
-if [[ "$isNinja" == "yes" ]]; then
-    cmake "${cmakeOptions[@]}" -B "${buildDir}" .
-    cd "${buildDir}"
-    CLICOLOR_FORCE=1 ninja build_and_test
-    exit 0
-fi
 cmake "${cmakeOptions[@]}" -B "${buildDir}" .
 time cmake --build "${buildDir}" -j "${numThreads}"