From bbdf4af98fbcef7bf8267e35037efae51edbc7eb Mon Sep 17 00:00:00 2001
From: Jason Rhinelander <jason@imaginary.ca>
Date: Wed, 30 Mar 2022 16:09:40 -0300
Subject: [PATCH] cmake work-around for cmake < 3.21

PkgConfig::xyz won't exist before 3.21 if xyz doesn't require any flags
(which is common for a system-installed header-only library like oxenc).

(CMake bug 22180)
---
 CMakeLists.txt | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index baef9ef..41fdebc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -76,7 +76,10 @@ elseif(BUILD_SHARED_LIBS)
     pkg_check_modules(oxenc liboxenc IMPORTED_TARGET)
 
     if(oxenc_FOUND)
-        target_link_libraries(oxenmq PUBLIC PkgConfig::oxenc)
+        # Work around cmake bug 22180 (PkgConfig::tgt not set if no flags needed)
+        if(TARGET PkgConfig::oxenc OR CMAKE_VERSION VERSION_GREATER_EQUAL "3.21")
+            target_link_libraries(oxenmq PUBLIC PkgConfig::oxenc)
+        endif()
     else()
         add_subdirectory(oxen-encoding)
         target_link_libraries(oxenmq PUBLIC oxenc)