tools: ctl: drop build-tree RUNPATH from sof-ctl

sof-ctl adds tools/lib as a link directory so it can link against a
locally built ALSA. CMake also embeds that directory in the ELF
RPATH/RUNPATH, so the binary carries a reference into the build tree.
On install the path is stripped to an empty string, which leaves an
empty DT_RUNPATH tag behind. Distro ELF security scanners reject that:
scanelf reports "Security problem NULL DT_RUNPATH".

Keep tools/lib as a -L link path only: skip the build RPATH and keep
the install RPATH empty so no DT_RUNPATH tag is emitted at all. The
installed binary resolves libasound through the normal loader search
path.

Link: #10070
Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Author: lrgirdwo

tools/ctl/CMakeLists.txt

@@ -11,6 +11,16 @@ target_link_libraries(sof-ctl PRIVATE
 	"-lasound"
 )
 
+# tools/lib is only needed as a -L link path for a locally built ALSA.
+# Do not let CMake also embed it as an ELF RPATH/RUNPATH: it points into
+# the build tree and, once stripped to empty on install, leaves an empty
+# DT_RUNPATH tag that trips distro ELF security scanners (scanelf reports
+# "NULL DT_RUNPATH"). Skip the build RPATH and keep the install RPATH
+# empty so no DT_RUNPATH tag is emitted. See thesofproject/sof#10070.
+set_target_properties(sof-ctl PROPERTIES
+	SKIP_BUILD_RPATH TRUE
+	INSTALL_RPATH "")
+
 target_compile_options(sof-ctl PRIVATE
 	-Wall -Werror
 )