From 26d2755d7c3181e90e46014778941bff53d2309f Mon Sep 17 00:00:00 2001
From: Peter Wu <peter@lekensteyn.nl>
Date: Thu, 4 Jun 2020 11:28:01 +0200
Subject: [PATCH] CMake: ignore INTERFACE_LIBRARY targets for pkg-config file

Reviewed-by: Marcel Raad
Fixes #5512
Closes #5517
---
 CMakeLists.txt | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a13395db7..5a1333397 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1413,7 +1413,15 @@ set(libdir                  "${CMAKE_INSTALL_PREFIX}/lib")
 foreach(_lib ${CMAKE_C_IMPLICIT_LINK_LIBRARIES} ${CURL_LIBS})
   if(TARGET "${_lib}")
     set(_libname "${_lib}")
-    get_target_property(_lib "${_lib}" LOCATION)
+    get_target_property(_libtype "${_libname}" TYPE)
+    if(_libtype STREQUAL INTERFACE_LIBRARY)
+      # Interface libraries can occur when an external project embeds curl and
+      # defined targets such as ZLIB::ZLIB by themselves. Ignore these as
+      # reading the LOCATION property will error out. Assume the user won't need
+      # this information in the .pc file.
+      continue()
+    endif()
+    get_target_property(_lib "${_libname}" LOCATION)
     if(NOT _lib)
       message(WARNING "Bad lib in library list: ${_libname}")
       continue()