Move jit removal logic for s390x to before_install

`default_configure_options.*` does not handle arch-specific logic.

Author: BanzaiMan

.travis.yml

@@ -119,6 +119,7 @@ jobs:
               eval "$(phpenv init -)"
             fi
           fi
+        - 'echo "--without-pcre-jit" >> $TRAVIS_BUILD_DIR/custom_configure_options'
     - arch: s390x
       dist: xenial
       group: edge
@@ -141,6 +142,7 @@ jobs:
               eval "$(phpenv init -)"
             fi
           fi
+        - 'echo "--without-pcre-jit" >> $TRAVIS_BUILD_DIR/custom_configure_options'
     - arch: arm64
       dist: bionic
       language: minimal