add package for add-apt-repository command

.drone.yml

@@ -182,8 +182,9 @@ steps:
     COMMON_FLAGS: 'USE_OPENMP=1'
   commands:
     - echo "MAKE_FLAGS:= $COMMON_FLAGS"
-    - add-apt-repository ppa:ubuntu-toolchain-r/ppa
     - apt-get update -y
+    - apt-get install -y software-properties-common
+    - add-apt-repository ppa:ubuntu-toolchain-r/ppa
     - apt-get install -y make $CC gfortran-10 perl python g++-10
     - $CC --version
     - make QUIET_MAKE=1 $COMMON_FLAGS -j