[libxslt] Check if variables exist when defining targets

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 74e4d86699e76f687ff2e65acd486a8d0ef282c9
Author: Markus Rickert <rickert fortiss org>
Date:   Thu Dec 31 13:48:43 2020 +0100

    Check if variables exist when defining targets

 libxslt-config.cmake.in | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/libxslt-config.cmake.in b/libxslt-config.cmake.in
index 89442473..1fb65624 100644
--- a/libxslt-config.cmake.in
+++ b/libxslt-config.cmake.in
@@ -99,7 +99,7 @@ endif()
 
 mark_as_advanced(LIBXSLT_LIBRARY LIBXSLT_EXSLT_LIBRARY LIBXSLT_XSLTPROC_EXECUTABLE)
 
-if(NOT TARGET LibXslt::LibXslt)
+if(NOT TARGET LibXslt::LibXslt AND DEFINED LIBXSLT_LIBRARY AND DEFINED LIBXSLT_INCLUDE_DIRS)
   add_library(LibXslt::LibXslt UNKNOWN IMPORTED)
   set_target_properties(LibXslt::LibXslt PROPERTIES IMPORTED_LOCATION "${LIBXSLT_LIBRARY}")
   set_target_properties(LibXslt::LibXslt PROPERTIES INTERFACE_COMPILE_OPTIONS "${LIBXSLT_DEFINITIONS}")
@@ -107,7 +107,7 @@ if(NOT TARGET LibXslt::LibXslt)
   set_target_properties(LibXslt::LibXslt PROPERTIES INTERFACE_LINK_LIBRARIES 
"${LIBXSLT_INTERFACE_LINK_LIBRARIES}")
 endif()
 
-if(NOT TARGET LibXslt::LibExslt)
+if(NOT TARGET LibXslt::LibExslt AND DEFINED LIBXSLT_EXSLT_LIBRARY AND DEFINED LIBXSLT_EXSLT_INCLUDE_DIRS)
   add_library(LibXslt::LibExslt UNKNOWN IMPORTED)
   set_target_properties(LibXslt::LibExslt PROPERTIES IMPORTED_LOCATION "${LIBXSLT_EXSLT_LIBRARY}")
   set_target_properties(LibXslt::LibExslt PROPERTIES INTERFACE_COMPILE_OPTIONS 
"${LIBXSLT_EXSLT_DEFINITIONS}")
@@ -115,7 +115,7 @@ if(NOT TARGET LibXslt::LibExslt)
   set_target_properties(LibXslt::LibExslt PROPERTIES INTERFACE_LINK_LIBRARIES 
"${LIBXSLT_EXSLT_INTERFACE_LINK_LIBRARIES}")
 endif()
 
-if(NOT TARGET LibXslt::xsltproc)
+if(NOT TARGET LibXslt::xsltproc AND DEFINED LIBXSLT_XSLTPROC_EXECUTABLE)
   add_executable(LibXslt::xsltproc IMPORTED)
   set_target_properties(LibXslt::xsltproc PROPERTIES IMPORTED_LOCATION "${LIBXSLT_XSLTPROC_EXECUTABLE}")
 endif()