Install usrmerge on ubuntu (needed for RTEMS builds)

- travis: only do that for RTEMS
  (as precise & trusty don't have usrmerge)
- gitlab: use focal instead
  (apt install usrmerge doesn't work in Docker)

.gitlab-ci.yml

@@ -137,12 +137,14 @@ wine64_static_debug:
 # Cross-builds to RTEMS 4.9 and 4.10
 rtems4.9_default:
   extends: .build
+  image: ubuntu:focal
   variables:
     RTEMS: "4.9"
     BASE: "3.15"
 
 rtems4.9_debug:
   extends: .build
+  image: ubuntu:focal
   variables:
     RTEMS: "4.9"
     BASE: "3.15"
@@ -150,11 +152,13 @@ rtems4.9_debug:
 
 rtems4.10_default:
   extends: .build
+  image: ubuntu:focal
   variables:
     RTEMS: "4.10"
 
 rtems4.10_debug:
   extends: .build
+  image: ubuntu:focal
   variables:
     RTEMS: "4.10"
     BCFG: "debug"

.travis.yml

@@ -143,11 +143,11 @@ jobs:
   - env: SET=test01 WINE=64 TEST=NO BCFG=debug
   - env: SET=test01 WINE=64 TEST=NO BCFG=static-debug
 
-  - env: SET=test01 RTEMS=4.9 BASE=3.15 TEST=NO
-  - env: SET=test01 RTEMS=4.9 BASE=3.15 TEST=NO BCFG=debug
+  - env: SET=test01 RTEMS=4.9 BASE=3.15 TEST=NO APT=usrmerge
+  - env: SET=test01 RTEMS=4.9 BASE=3.15 TEST=NO BCFG=debug APT=usrmerge
 
-  - env: SET=test01 RTEMS=4.10
-  - env: SET=test01 RTEMS=4.10 BCFG=debug
+  - env: SET=test01 RTEMS=4.10 APT=usrmerge
+  - env: SET=test01 RTEMS=4.10 BCFG=debug APT=usrmerge
 
   - env: SET=test01
     os: windows

travis/.travis.yml.example-full

@@ -104,9 +104,9 @@ jobs:
 
 # Cross-compilation to RTEMS
 
-  - env: BASE=7.0 RTEMS=4.10
+  - env: BASE=7.0 RTEMS=4.10 APT=usrmerge
 
-  - env: BASE=7.0 RTEMS=4.9
+  - env: BASE=7.0 RTEMS=4.9 APT=usrmerge
 
 # Other gcc versions (added as an extra package)