[CMake] Add support for building on illumos (#74930)

illumos has an older version of the Solaris linker that does not
support the GNU version script compat nor version scripts and does
not support -Bsymbolic-functions. Treat illumos linker separately.

The libclang/CMakeLists part lifted from NetBSD's pkgsrc.

Build tested on Solaris 11.4 and OpenIndiana 2023.10.

/usr/bin/ld --version

ld: Software Generation Utilities - Solaris Link Editors: 5.11-1.3260

ld: Software Generation Utilities - Solaris Link Editors: 5.11-1.1790 (illumos)

4 files changed, 23 insertions, 6 deletions

diff --git a/clang/tools/clang-shlib/CMakeLists.txt b/clang/tools/clang-shlib/CMakeLists.txt
index aa7fcd1..298d3a9 100644
--- a/clang/tools/clang-shlib/CMakeLists.txt
+++ b/clang/tools/clang-shlib/CMakeLists.txt
@@ -50,7 +50,7 @@ add_clang_library(clang-cpp
                   ${_DEPS})
 # Optimize function calls for default visibility definitions to avoid PLT and
 # reduce dynamic relocations.
-if (NOT APPLE AND NOT MINGW)
+if (NOT APPLE AND NOT MINGW AND NOT LLVM_LINKER_IS_SOLARISLD_ILLUMOS)
   target_link_options(clang-cpp PRIVATE LINKER:-Bsymbolic-functions)
 endif()
 if (MINGW OR CYGWIN)
diff --git a/clang/tools/libclang/CMakeLists.txt b/clang/tools/libclang/CMakeLists.txt
index 4f23065..1cfc46e 100644
--- a/clang/tools/libclang/CMakeLists.txt
+++ b/clang/tools/libclang/CMakeLists.txt
@@ -185,11 +185,22 @@ if(ENABLE_SHARED)
     endif()
   endif()
   if (USE_VERSION_SCRIPT)
-    target_link_options(libclang PRIVATE "-Wl,--version-script,${CMAKE_CURRENT_SOURCE_DIR}/libclang.map")
-    # The Solaris 11.4 linker supports a subset of GNU ld version scripts,
-    # but requires a special option to enable it.
     if (${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
-      target_link_options(libclang PRIVATE "-Wl,-z,gnu-version-script-compat")
+      include(CheckLinkerFlag)
+      # The Solaris 11.4 linker supports a subset of GNU ld version scripts,
+      # but requires a special option to enable it.
+      llvm_check_linker_flag(CXX "-Wl,-z,gnu-version-script-compat"
+                             LINKER_SUPPORTS_Z_GNU_VERSION_SCRIPT_COMPAT)
+      # Older Solaris (and illumos) linker does not support GNU ld version scripts
+      # and does not support GNU version script compat.
+      if (LINKER_SUPPORTS_Z_GNU_VERSION_SCRIPT_COMPAT)
+        target_link_options(libclang PRIVATE "-Wl,--version-script,${CMAKE_CURRENT_SOURCE_DIR}/libclang.map")
+        target_link_options(libclang PRIVATE "-Wl,-z,gnu-version-script-compat")
+      else()
+        target_link_options(libclang PRIVATE "-Wl,-M,${CMAKE_CURRENT_SOURCE_DIR}/libclang.map")
+      endif()
+    else()
+      target_link_options(libclang PRIVATE "-Wl,--version-script,${CMAKE_CURRENT_SOURCE_DIR}/libclang.map")
     endif()
     # Ensure that libclang.so gets rebuilt when the linker script changes.
     set_property(SOURCE ARCMigrate.cpp APPEND PROPERTY
diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index c9bca30..14c0837 100644
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -241,6 +241,12 @@ if (NOT DEFINED LLVM_LINKER_DETECTED AND NOT WIN32)
       set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")
       set(LLVM_LINKER_IS_GNULD YES CACHE INTERNAL "")
       message(STATUS "Linker detection: GNU ld")
+    elseif("${stderr}" MATCHES "(illumos)" OR
+           "${stdout}" MATCHES "(illumos)")
+      set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")
+      set(LLVM_LINKER_IS_SOLARISLD YES CACHE INTERNAL "")
+      set(LLVM_LINKER_IS_SOLARISLD_ILLUMOS YES CACHE INTERNAL "")
+      message(STATUS "Linker detection: Solaris ld (illumos)")
     elseif("${stderr}" MATCHES "Solaris Link Editors" OR
            "${stdout}" MATCHES "Solaris Link Editors")
       set(LLVM_LINKER_DETECTED YES CACHE INTERNAL "")
diff --git a/llvm/tools/llvm-shlib/CMakeLists.txt b/llvm/tools/llvm-shlib/CMakeLists.txt
index 64d6f63..a47a0ec 100644
--- a/llvm/tools/llvm-shlib/CMakeLists.txt
+++ b/llvm/tools/llvm-shlib/CMakeLists.txt
@@ -49,7 +49,7 @@ if(LLVM_BUILD_LLVM_DYLIB)
       # Solaris ld does not accept global: *; so there is no way to version *all* global symbols
       set(LIB_NAMES -Wl,--version-script,${LLVM_LIBRARY_DIR}/tools/llvm-shlib/simple_version_script.map ${LIB_NAMES})
     endif()
-    if (NOT MINGW)
+    if (NOT MINGW AND NOT LLVM_LINKER_IS_SOLARISLD_ILLUMOS)
       # Optimize function calls for default visibility definitions to avoid PLT and
       # reduce dynamic relocations.
       # Note: for -fno-pic default, the address of a function may be different from