.cirrus.yml: add bash to the brew packages

Like the sed we include earlier we want something more recent for
iotests to work.

Fixes: 57ee95ed
Cc: Max Reitz <mreitz@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20200710182238.10675-1-alex.bennee@linaro.org>

.cirrus.yml

@@ -20,7 +20,7 @@ macos_task:
   osx_instance:
     image: mojave-base
   install_script:
-    - brew install pkg-config python gnu-sed glib pixman make sdl2
+    - brew install pkg-config python gnu-sed glib pixman make sdl2 bash
   script:
     - mkdir build
     - cd build
@@ -33,7 +33,7 @@ macos_xcode_task:
     # this is an alias for the latest Xcode
     image: mojave-xcode
   install_script:
-    - brew install pkg-config gnu-sed glib pixman make sdl2
+    - brew install pkg-config gnu-sed glib pixman make sdl2 bash
   script:
     - mkdir build
     - cd build