Update the Dockerfile to use /

```
Step 6/13 : ADD *.patch /root/rpmbuild/SOURCES
When using ADD with more than one source file, the destination must be a directory and end with a /
```

Author: shahmishal

platforms/Linux/Fedora/Dockerfile

@@ -5,7 +5,7 @@ WORKDIR /root
 
 RUN mkdir -p /root/rpmbuild/{BUILD,RPMS,SOURCES,SPECS,SRPMS}
 ADD swift-lang.spec /root/rpmbuild/SPECS/swift-lang.spec
-ADD *.patch /root/rpmbuild/SOURCES
+ADD *.patch /root/rpmbuild/SOURCES/
 
 ADD build_swift_rpm.sh /root/build_swift_rpm.sh
 RUN chmod +x /root/build_swift_rpm.sh