Improve build.sh speed (#2521)

By default build and pack will trigger restore and build respectively.
Considering it was just built and restored, no need to repeat these
steps. Thus adding option to disable this in each step.

build.sh

@@ -21,7 +21,7 @@ build() {
   echo -e "Build ...... "
   echo -e "===========================================================\n"
 
-  dotnet build WilsonUnix.sln
+  dotnet build --no-restore WilsonUnix.sln
   echo -e "\n"
 }
 
@@ -30,7 +30,7 @@ pack() {
   echo -e "Pack ...... "
   echo -e "===========================================================\n"
 
-  dotnet pack WilsonUnix.sln
+  dotnet pack --no-build WilsonUnix.sln
 
   echo -e "\n"
   echo -e "==========================================================="