bsdinstall.8: note that installerscript variables must be exported

[asomers]

Summary

Reported by: jlduran
MFC after: 1 week

Test Plan

Doc change only

[jlduran]

Hmm, I was about to submit a change that:

--- a/usr.sbin/bsdinstall/scripts/script
+++ b/usr.sbin/bsdinstall/scripts/script
@@ -50,6 +50,7 @@ f_include $BSDCFG_SHARE/variable.subr
 ############################################################ GLOBALS

 : ${TMPDIR:="/tmp"}
+: ${DISTRIBUTIONS=""}; export DISTRIBUTIONS

 #
 # Strings that should be moved to an i18n file and loaded with f_include_lang()

In my opinion is a "better" fix.

[asomers]

In D57318#1313384, @jlduran wrote:

Hmm, I was about to submit a change that:

--- a/usr.sbin/bsdinstall/scripts/script
+++ b/usr.sbin/bsdinstall/scripts/script
@@ -50,6 +50,7 @@ f_include $BSDCFG_SHARE/variable.subr
 ############################################################ GLOBALS

 : ${TMPDIR:="/tmp"}
+: ${DISTRIBUTIONS=""}; export DISTRIBUTIONS

 #
 # Strings that should be moved to an i18n file and loaded with f_include_lang()

In my opinion is a "better" fix.

Yeah, I like that too, if it means that the user doesn't need to care.

[jlduran]

Also, note that PARTITIONS is not used in any other script, so there is no need to export (there has never been the need to export it either).