Change default PREFIX to /opt/local

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

rocky9/Dockerfile

@@ -38,10 +38,10 @@ RUN dnf install --assumeyes --enablerepo=crb \
 RUN git config --global url."https://wangguofang.net/github.com/".insteadOf "https://github.com/"
 
 # Install prefix of every dependency. Libraries are installed under ${PREFIX}/lib64.
-ARG PREFIX=/usr/local
+ARG PREFIX=/opt/local
 
 # Make the compiler, CMake, pkg-config and the shell find earlier dependencies under a prefix other
-# than the default /usr/local. CMake (>= 3.29) takes its default install prefix from the environment.
+# than the default /opt/local. CMake (>= 3.29) takes its default install prefix from the environment.
 ENV PATH=${PREFIX}/bin:${PATH} \
     C_INCLUDE_PATH=${PREFIX}/include \
     CPLUS_INCLUDE_PATH=${PREFIX}/include \