[llvm] Add -lpthread for powerpc64le shared libs build (PR #132265)

[Zarko Todorovski via llvm-commits]

https://github.com/ZarkoT created https://github.com/llvm/llvm-project/pull/132265

Fixes the ppc64le shared libs build: https://lab.llvm.org/buildbot/#/builders/145/builds/5759/steps/5/logs/stdio

This may be overkill and I'm open to suggestions on making this more specific. 

>From 7551787b4d3ea2a4c7bf79d4f033639fc2919471 Mon Sep 17 00:00:00 2001
From: Zarko Todorovski <zarko at ca.ibm.com>
Date: Thu, 20 Mar 2025 14:02:54 -0400
Subject: [PATCH] Add -lpthread for powerpc64le build

---
 llvm/cmake/modules/HandleLLVMOptions.cmake | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
index 185c9b63aada3..7f4d578525860 100644
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -1320,6 +1320,13 @@ if(LLVM_LINK_LLVM_DYLIB AND LLVM_EXPORT_SYMBOLS_FOR_PLUGINS)
   message(FATAL_ERROR "LLVM_LINK_LLVM_DYLIB not compatible with LLVM_EXPORT_SYMBOLS_FOR_PLUGINS")
 endif()
 
+#The shared libs build for Linux on PowerPC requires -lpthread
+if(BUILD_SHARED_LIBS AND ${CMAKE_SYSTEM_NAME} MATCHES "Linux" AND LLVM_HOST_TRIPLE MATCHES "powerpc*")
+    append("-lpthread"
+           CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
+endif()
+
+
 # By default we should enable LLVM_ENABLE_IDE only for multi-configuration
 # generators. This option disables optional build system features that make IDEs
 # less usable.