Set tools and tests rpath on Linux. (#804)

Fixes #796.

Author: MarkCallow

tests/CMakeLists.txt

@@ -2,10 +2,15 @@
 # SPDX-License-Identifier: Apache-2.0
 
 function(set_test_properties test_target)
+    # See comments in set_tools_properties() in ../tools/CMakeLists.txt.
     if(APPLE)
         set_target_properties(${test_target} PROPERTIES
             INSTALL_RPATH "@executable_path;/usr/local/lib"
         )
+    elseif(LINUX)
+        set_target_properties(${test_target} PROPERTIES
+            INSTALL_RPATH "$ORIGIN;$ORIGIN/../lib"
+        )
     endif()
 endfunction()
 

tools/CMakeLists.txt

@@ -15,9 +15,35 @@ function(set_tool_properties tool_target)
     if(APPLE)
         set_target_properties(${tool_target} PROPERTIES
             XCODE_ATTRIBUTE_ENABLE_HARDENED_RUNTIME "YES"
+            # Creates an LC_RPATH entry in the Mac-O binary for each
+            # item in this list. When searching for libraries whose
+            # install name starts with @rpath, as libktx's does, dyld
+            # searches each LC_RPATH in the order given here.
+            #
+            # Check the LC_RPATH entries with
+            # - otool -l <file> | grep -A 3 LC_RPATH
+            #
+            # TODO: Consider adding @executable_path/../lib.
             INSTALL_RPATH "@executable_path;/usr/local/lib"
             CXX_VISIBILITY_PRESET ${STATIC_APP_LIB_SYMBOL_VISIBILITY}
         )
+    elseif(LINUX)
+        set_target_properties(${tool_target} PROPERTIES
+            # With modern tools sets DT_RUNPATH not the deprecated
+            # DT_RPATH in ELF binaries.  ld.so searches for libraries
+            # as follows:
+            # - LD_LIBRARY_PATH
+            # - RUNPATH
+            # - Directories given in /etc/ld.so.conf.
+            #   /usr/local/lib is listed there.
+            # - Default path: /lib;/usr/lib.
+            # $ORIGIN is equivalent to @executable_path.
+            #
+            # Check DT_RUNPATH with one of
+            # - readelf -d <file> | head -20
+            # - objdump -x <file> | grep 'R.*PATH'
+            INSTALL_RPATH "$ORIGIN;$ORIGIN/../lib"
+        )
     endif()
 endfunction()