Merge pull request #31647 from gottesmm/pr-ff0d585699a2dcf98bf6077190a869f014d0fec0

[build-script] On non-Darwin build lld by default.

Author: gottesmm

utils/build-script-impl

@@ -125,6 +125,7 @@ KNOWN_SETTINGS=(
     skip-build-benchmarks                         ""                "set to skip building Swift Benchmark Suite"
     skip-build-clang-tools-extra                  ""                "set to skip building clang-tools-extra as part of llvm"
     skip-build-compiler-rt                        ""                "set to skip building Compiler-RT"
+    skip-build-lld                                ""                "set to skip building lld as part of llvm (linux only)"
     skip-build-cygwin                             ""                "set to skip building Swift stdlibs for Cygwin"
     skip-build-external-benchmarks                "1"               "set to skip building the external Swift Benchmark Suite. (skipped by default)"
     skip-build-freebsd                            ""                "set to skip building Swift stdlibs for FreeBSD"
@@ -1490,6 +1491,7 @@ for host in "${ALL_HOSTS[@]}"; do
                     -DCMAKE_CXX_FLAGS_RELWITHDEBINFO="-O2 -DNDEBUG"
                     -DCMAKE_BUILD_TYPE:STRING="${LLVM_BUILD_TYPE}"
                     -DLLVM_TOOL_SWIFT_BUILD:BOOL=NO
+                    -DLLVM_TOOL_LLD_BUILD:BOOL=TRUE
                     -DLLVM_INCLUDE_DOCS:BOOL=TRUE
                     -DLLVM_ENABLE_LTO:STRING="${LLVM_ENABLE_LTO}"
                     -DCOMPILER_RT_INTERCEPT_LIBDISPATCH=ON
@@ -1506,12 +1508,20 @@ for host in "${ALL_HOSTS[@]}"; do
                     llvm_enable_projects+=("clang-tools-extra")
                 fi
 
-                cmake_options+=(
-                    -DLLVM_ENABLE_PROJECTS="$(join ";" ${llvm_enable_projects[@]})"
-                )
+                # On non-Darwin platforms, build lld so we can always have a
+                # linker that is compatible with the swift we are using to
+                # compile the stdlib.
+                #
+                # This makes it easier to build target stdlibs on systems that
+                # have old toolchains without more modern linker features.
+                if [[ "$(uname -s)" != "Darwin" ]] ; then
+                    if [[ ! "${SKIP_BUILD_LLD}" ]]; then
+                        llvm_enable_projects+=("lld")
+                    fi
+                fi
 
                 cmake_options+=(
-                  -DLLVM_TOOL_LLD_BUILD:BOOL=TRUE
+                    -DLLVM_ENABLE_PROJECTS="$(join ";" ${llvm_enable_projects[@]})"
                 )
 
                 if [[ "${BUILD_TOOLCHAIN_ONLY}" ]]; then