README: Make sure to use module purge

To avoid `sh_to_modulefile` to pick up current `LD_LIBRARY_PATH`, make sure to use `module purge` first.

CBI/scl-devtoolset/README.md

@@ -44,18 +44,13 @@ export PKG_CONFIG_PATH=/opt/rh/devtoolset-9/root/usr/lib64/pkgconfig${PKG_CONFIG
 This script can be transpiled to Lmod commands as:
 
 ```lua
-$ "${LMOD_DIR}/sh_to_modulefile" /opt/rh/devtoolset-9/enable
-prepend_path("INFOPATH","/opt/rh/devtoolset-9/root/usr/share/info")
-prepend_path("LD_LIBRARY_PATH","/opt/rh/devtoolset-9/root/usr/lib/dyninst")
-prepend_path("LD_LIBRARY_PATH","/opt/rh/devtoolset-9/root/usr/lib64/dyninst")
-prepend_path("LD_LIBRARY_PATH","/opt/rh/devtoolset-9/root/usr/lib")
-prepend_path("LD_LIBRARY_PATH","/opt/rh/devtoolset-9/root/usr/lib64")
-append_path("LD_LIBRARY_PATH","/usr/lib64/openmpi/lib")
-append_path("LD_LIBRARY_PATH","/opt/rh/devtoolset-8/root/usr/lib")
+$ (module purge; "${LMOD_DIR}/sh_to_modulefile" /opt/rh/devtoolset-9/enable)
+setenv("INFOPATH","/opt/rh/devtoolset-9/root/usr/share/info")
+setenv("LD_LIBRARY_PATH","/opt/rh/devtoolset-9/root/usr/lib64:/opt/rh/devtoolset-9/root/usr/lib:/opt/rh/devtoolset-9/root/usr/lib64/dyninst:/opt/rh/devtoolset-9/root/usr/lib/dyninst:/opt/rh/devtoolset-9/root/usr/lib64:/opt/rh/devtoolset-9/root/usr/lib")
 prepend_path("MANPATH","/opt/rh/devtoolset-9/root/usr/share/man")
 prepend_path("PATH","/opt/rh/devtoolset-9/root/usr/bin")
 setenv("PCP_DIR","/opt/rh/devtoolset-9/root")
-prepend_path("PKG_CONFIG_PATH","/opt/rh/devtoolset-9/root/usr/lib64/pkgconfig")
+setenv("PKG_CONFIG_PATH","/opt/rh/devtoolset-9/root/usr/lib64/pkgconfig")
 ```
 
 With these commands, we can create an module environment file.  See [CBI/scl-devtoolset/9.lua](9.lua) for an example.