ci: Travis: move coverage job to first stage (neovim#10673)

This swaps it with "gcc-32bit".
It is better to have the "coverage" job run than "gcc-32bit" in case of
flaky build failures - especially on master, since otherwise no base
coverage is available for future PRs.

.travis.yml

@@ -100,16 +100,21 @@ jobs:
         - CMAKE_FLAGS="$CMAKE_FLAGS -DPREFER_LUA=ON"
         - DEPS_CMAKE_FLAGS="$DEPS_CMAKE_FLAGS -DUSE_BUNDLED_LUAJIT=OFF"
         - *common-job-env
-    - name: gcc-32bit
+    - name: gcc-coverage (gcc 9)
       os: linux
-      # Travis creates a cache per compiler. Set a different value here to
-      # store 32-bit dependencies in a separate cache.
-      compiler: gcc
+      compiler: gcc-9
       env:
-        - BUILD_32BIT=ON
-        # Minimum required CMake.
-        - CMAKE_URL=https://cmake.org/files/v2.8/cmake-2.8.12-Linux-i386.sh
+        - GCOV=gcov-9
+        - CMAKE_FLAGS="$CMAKE_FLAGS -DUSE_GCOV=ON"
+        - GCOV_ERROR_FILE="/tmp/libgcov-errors.log"
         - *common-job-env
+      addons:
+        apt:
+          sources:
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+          packages:
+            - *common-apt-packages
+            - gcc-9
     - if: branch = master AND commit_message !~ /\[skip.lint\]/
       name: lint
       os: linux
@@ -125,21 +130,16 @@ jobs:
       env:
         - *common-job-env
 
-    - name: gcc-coverage (gcc 9)
+    - name: gcc-32bit
       os: linux
-      compiler: gcc-9
+      # Travis creates a cache per compiler. Set a different value here to
+      # store 32-bit dependencies in a separate cache.
+      compiler: gcc
       env:
-        - GCOV=gcov-9
-        - CMAKE_FLAGS="$CMAKE_FLAGS -DUSE_GCOV=ON"
-        - GCOV_ERROR_FILE="/tmp/libgcov-errors.log"
+        - BUILD_32BIT=ON
+        # Minimum required CMake.
+        - CMAKE_URL=https://cmake.org/files/v2.8/cmake-2.8.12-Linux-i386.sh
         - *common-job-env
-      addons:
-        apt:
-          sources:
-            - sourceline: 'ppa:ubuntu-toolchain-r/test'
-          packages:
-            - *common-apt-packages
-            - gcc-9
 
     - name: clang-tsan
       os: linux