pkg/56165: Add strnlen to _OPSYS_MISSING_FEATURES on Solaris < 5.11

[pekdon%gmail.com@localhost]

>Number:         56165
>Category:       pkg
>Synopsis:       Add strnlen to _OPSYS_MISSING_FEATURES on Solaris < 5.11
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri May 14 10:45:00 +0000 2021
>Originator:     Claes Nästén
>Release:        trunk 2021-05-14
>Organization:
>Environment:
SunOS u40 5.10 Generic_147148-26 i86pc i386 i86pc

>Description:
Solaris prior to 5.11 does not have strnlen available, add it to the list of missing features to trigger use of libnbcompat where required.

See attached diff for proposed solution.
>How-To-Repeat:
Build a port with USE_FEATURES = strnlen
>Fix:
diff --git a/mk/platform/SunOS.mk b/mk/platform/SunOS.mk
index fc24dda23bd..ca212a241ab 100644
--- a/mk/platform/SunOS.mk
+++ b/mk/platform/SunOS.mk
@@ -72,6 +72,9 @@ _OPSYS_MISSING_FEATURES=asprintf
 .if !exists(/usr/include/err.h)
 _OPSYS_MISSING_FEATURES+=err
 .endif
+.if ${OS_VARIANT} == "Solaris" && (!empty(OS_VERSION:M5.[0-9]) || ${OS_VERSION} == "5.10")
+_OPSYS_MISSING_FEATURES+=strnlen
+.endif
 _PATCH_CAN_BACKUP=     yes             # native patch(1) can make backups
 _PATCH_BACKUP_ARG?=    -b -V simple -z # switch to patch(1) for backup suffix
 _USE_RPATH=            yes             # add rpath to LDFLAGS