From https://github.com/NationalSecurityAgency/ghidra/pull/490

Index: GPL/DemanglerGnu/build.gradle
--- GPL/DemanglerGnu/build.gradle.orig
+++ GPL/DemanglerGnu/build.gradle
@@ -83,6 +83,8 @@ model {
 			targetPlatform "mac_arm_64"
 			targetPlatform "freebsd_x86_64"
 			targetPlatform "freebsd_arm_64"
+			targetPlatform "openbsd_x86_64"
+			targetPlatform "openbsd_arm_64"
 			sources {
 				c {
 					source {
@@ -106,6 +108,8 @@ model {
 			targetPlatform "mac_arm_64"
 			targetPlatform "freebsd_x86_64"
 			targetPlatform "freebsd_arm_64"
+			targetPlatform "openbsd_x86_64"
+			targetPlatform "openbsd_arm_64"
 			sources {
 				c {
 					source {
