profile: avoid to repeat many times same PATH info

profile

 # PATH system
 
 # Rust
-export PATH="${HOME}/.cargo/bin:${PATH}"
+PREFIX_PATH="${HOME}/.cargo/bin"
 
 # Ruby
-export PATH="${HOME}/.local/share/gem/ruby/2.7.0/bin:${PATH}"
+PREFIX_PATH="${HOME}/.gem/ruby/2.3.0/bin:${PREFIX_PATH}"
+PREFIX_PATH="${HOME}/.local/share/gem/ruby/2.7.0/bin:${PREFIX_PATH}"
 
 # Manually installed binaries
+PREFIX_PATH="${HOME}/.local/bin:${PREFIX_PATH}"
 export LD_LIBRARY_PATH="${HOME}/.local/lib/x86_64-linux-gnu/:${LD_LIBRARY_PATH}"
-export PATH="${HOME}/.local/bin:${PATH}"
+
+# Finally add prefix to PATH
+export PATH="${PREFIX_PATH}:${PATH}"