Travis: fix the build

1. The polyfill `master` branches have been renamed to `main`.
2. There's been a snafu in the Polyfill meta-repo.
    They've updated the minimum PHP version to PHP 7.1 and intended to make the polyfills for PHP < 7.2 stand-alone, but they actually rolled the minimum change out to the packages and tagged a release, which makes any version of the polyfills for PHP < 7.2 useless as they can no longer be installed. _sigh_
    Left a comment in the PR upstream. Hopefully they'll fix this in one way or another, but in the mean time, `1.19` is the last installable version of these polyfills.

I've fixed this for now by moving the `install` instructions to the jobs matrix and letting each build have its own variation to allow the packages to install.

Author: jrfnl

.travis.yml

@@ -17,10 +17,19 @@ matrix:
         apt:
           packages:
             - libxml2-utils
+      install:
+        - composer install
+
     - php: 5.4
+      install:
+        - composer require --no-update symfony/polyfill-php72:"1.19" symfony/polyfill-php73:"1.19" symfony/polyfill-php74:"1.19"
+        - composer install
 
     - php: 7.4
       env: PHPCOMPAT="dev-develop as 9.99.99"
+      install:
+        - composer config minimum-stability dev
+        - composer require --no-update phpcompatibility/php-compatibility:"${PHPCOMPAT}"
 
   allow_failures:
     # Allow failures for unstable builds.
@@ -30,12 +39,8 @@ before_install:
   # Speed up build time by disabling Xdebug when its not needed.
   - phpenv config-rm xdebug.ini || echo 'No xdebug config.'
   - export XMLLINT_INDENT="    "
-  - |
-    if [[ $PHPCOMPAT ]]; then
-      composer config minimum-stability dev
-      composer require --no-update phpcompatibility/php-compatibility:"${PHPCOMPAT}"
-    fi
-  - composer install
+
+before_script:
   - vendor/bin/phpcs -i
 
 script:

composer.json

@@ -24,14 +24,14 @@
   },
   "require-dev" : {
     "dealerdirect/phpcodesniffer-composer-installer": "^0.7",
-    "symfony/polyfill-php54": "dev-master",
-    "symfony/polyfill-php55": "dev-master",
-    "symfony/polyfill-php56": "dev-master",
-    "symfony/polyfill-php70": "dev-master",
-    "symfony/polyfill-php71": "dev-master",
-    "symfony/polyfill-php72": "dev-master",
-    "symfony/polyfill-php73": "dev-master",
-    "symfony/polyfill-php74": "dev-master"
+    "symfony/polyfill-php54": "1.19",
+    "symfony/polyfill-php55": "1.19",
+    "symfony/polyfill-php56": "1.19",
+    "symfony/polyfill-php70": "1.19",
+    "symfony/polyfill-php71": "1.19",
+    "symfony/polyfill-php72": "dev-main",
+    "symfony/polyfill-php73": "dev-main",
+    "symfony/polyfill-php74": "dev-main"
   },
   "suggest" : {
     "dealerdirect/phpcodesniffer-composer-installer": "^0.7 || This Composer plugin will sort out the PHP_CodeSniffer 'installed_paths' automatically.",