(PA-5632) Check for SELinux symlink

Prior to this commit, when building runtimes the SELinux component
created a symlink for a shared library on Red Hat 9 in order to
successfully build SELinux 3.3.

This worked for the agent runtimes but because the PDK runtime builds
multiple Rubies, builds would fail because it would attempt to create a
symlink when one already existed.

This commit checks for a symlink for the SELinux shared library before
creating one.

configs/components/_base-ruby-selinux.rb

@@ -71,7 +71,10 @@
   # libselinux 3.3 is the minimum version we want to build on RHEL 9, but the
   # libeselinux-devel-3.3 package confusingly installs a shared library that
   # uses 3.4. The hacky workaround for this is to symlink an existing library.
-  steps << 'ln -s /usr/lib64/libselinux.so.1 /usr/lib64/libselinux.so' if platform.name.start_with?('el-9')
+  # PDK builds two Rubies so check if symlink exists first.
+  if platform.name.start_with?('el-9')
+    steps << 'if [ ! -L /usr/lib64/libselinux.so ]; then ln -s /usr/lib64/libselinux.so.1 /usr/lib64/libselinux.so; fi'
+  end
 
   steps.concat([
     "#{cc} $${INCLUDESTR} #{system_include} #{cflags} -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -fPIC -DSHARED -c -o selinuxswig_ruby_wrap.lo selinuxswig_ruby_wrap.c",