package/llvm: remove $ORIGIN/../lib from RPATH

AddLLVM.cmake adds $ORIGIN/../lib to the RPATH of llvm binaries. This causes a problem when llvm-config from host installed in STAGING_DIR is executed under the following conditions:

*Target architecture same as host architecture (normally x86_64) *Target's libc different from host's libc (normally glibc)

llvm-config will try to link with the target's libc, resulting in:

./llvm-config: error while loading shared libraries: libc.so.0:
cannot open shared object file: No such file or directory.

Link to autobuild error:
http://autobuild.buildroot.net/results/b81c12d529c66a028e2297ea5ce1d6930324fa69/

To avoid this, add HOST_LLVM_CONF_OPTS += -DCMAKE_INSTALL_RPATH="$(HOST_DIR)/lib"

Link to discussion:
http://lists.busybox.net/pipermail/buildroot/2018-April/218627.html

---
Changes v1 -> v2:

Instead of patching AddLLVM.cmake, use CMAKE_INSTALL_RPATH option for host in llvm.mk

 package/llvm/llvm.mk | 6 ++++++
 1 file changed, 6 insertions(+)

index 8b88957203..3587b8af9d 100644
@@ -25,6 +25,12 @@ LLVM_CONF_OPTS += -DLLVM_ENABLE_PROJECTS=""
 HOST_LLVM_CONF_OPTS += -DLLVM_CCACHE_BUILD=$(if $(BR2_CCACHE),ON,OFF)
 LLVM_CONF_OPTS += -DLLVM_CCACHE_BUILD=$(if $(BR2_CCACHE),ON,OFF)
 
+# This option avoids AddLLVM.cmake from adding $ORIGIN/../lib
+# to binaries. Otherwise, llvm-config (host variant installed
+# in STAGING) will try to link with target's libc:
+# http://autobuild.buildroot.net/results/b81c12d529c66a028e2297ea5ce1d6930324fa69/
+HOST_LLVM_CONF_OPTS += -DCMAKE_INSTALL_RPATH="$(HOST_DIR)/lib"
+
 # Disable experimental Global Instruction Selection support.
 # https://llvm.org/docs/GlobalISel.html
 HOST_LLVM_CONF_OPTS += -DLLVM_BUILD_GLOBAL_ISEL=OFF

2.14.3

Hello,

Applied to master with some minor tweaks to the commit log and comment in the code. Thanks!

Thomas

Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com