diff --git a/compiler-rt/cmake/Modules/AddCompilerRT.cmake b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
--- a/compiler-rt/cmake/Modules/AddCompilerRT.cmake
+++ b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
@@ -83,8 +83,7 @@
         "${libname}" MATCHES ".*\.osx.*")
       foreach(arch ${LIB_ARCHS_${libname}})
         list(APPEND target_flags
-          -target ${arch}-apple-macos${DARWIN_osx_MIN_VER}
-          -darwin-target-variant ${arch}-apple-ios13.1-macabi)
+          "SHELL:-target ${arch}-apple-macos${DARWIN_osx_MIN_VER} -darwin-target-variant ${arch}-apple-ios13.1-macabi")
       endforeach()
     endif()
 
@@ -251,11 +250,9 @@
           "${os}" MATCHES "^(osx)$")
         foreach(arch ${LIB_ARCHS_${libname}})
           list(APPEND extra_cflags_${libname}
-            -target ${arch}-apple-macos${DARWIN_osx_MIN_VER}
-            -darwin-target-variant ${arch}-apple-ios13.1-macabi)
+            "SHELL:-target ${arch}-apple-macos${DARWIN_osx_MIN_VER} -darwin-target-variant ${arch}-apple-ios13.1-macabi")
           list(APPEND extra_link_flags_${libname}
-            -target ${arch}-apple-macos${DARWIN_osx_MIN_VER}
-            -darwin-target-variant ${arch}-apple-ios13.1-macabi)
+            "SHELL:-target ${arch}-apple-macos${DARWIN_osx_MIN_VER} -darwin-target-variant ${arch}-apple-ios13.1-macabi")
         endforeach()
       endif()
     endforeach()
diff --git a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
--- a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
+++ b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
@@ -304,8 +304,7 @@
       "${LIB_OS}" MATCHES "^osx$")
     # Build the macOS builtins with Mac Catalyst support.
     list(APPEND builtin_cflags
-      -target ${LIB_ARCH}-apple-macos${DARWIN_osx_BUILTIN_MIN_VER}
-      -darwin-target-variant ${LIB_ARCH}-apple-ios13.1-macabi)
+      "SHELL:-target ${LIB_ARCH}-apple-macos${DARWIN_osx_BUILTIN_MIN_VER} -darwin-target-variant ${LIB_ARCH}-apple-ios13.1-macabi")
   endif()
 
   set_target_compile_flags(${libname}
@@ -400,12 +399,12 @@
 macro(darwin_add_builtin_libraries)
   set(DARWIN_EXCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/Darwin-excludes)
 
-  set(CFLAGS "-fPIC -O3 -fvisibility=hidden -DVISIBILITY_HIDDEN -Wall -fomit-frame-pointer")
+  set(CFLAGS -fPIC -O3 -fvisibility=hidden -DVISIBILITY_HIDDEN -Wall -fomit-frame-pointer)
   set(CMAKE_C_FLAGS "")
   set(CMAKE_CXX_FLAGS "")
   set(CMAKE_ASM_FLAGS "")
 
-  append_string_if(COMPILER_RT_HAS_ASM_LSE " -DHAS_ASM_LSE" CFLAGS)
+  append_list_if(COMPILER_RT_HAS_ASM_LSE -DHAS_ASM_LSE CFLAGS)
 
   set(PROFILE_SOURCES ../profile/InstrProfiling.c
                       ../profile/InstrProfilingBuffer.c
@@ -515,7 +514,7 @@
 
     set(MACHO_SYM_DIR ${CMAKE_CURRENT_SOURCE_DIR}/macho_embedded)
 
-    set(CFLAGS "-Oz -Wall -fomit-frame-pointer -ffreestanding")
+    set(CFLAGS -Oz -Wall -fomit-frame-pointer -ffreestanding)
     set(CMAKE_C_FLAGS "")
     set(CMAKE_CXX_FLAGS "")
     set(CMAKE_ASM_FLAGS "")
@@ -534,8 +533,8 @@
     set(DARWIN_macho_embedded_LIBRARY_INSTALL_DIR
       ${COMPILER_RT_INSTALL_LIBRARY_DIR}/macho_embedded)
       
-    set(CFLAGS_armv7 "-target thumbv7-apple-darwin-eabi")
-    set(CFLAGS_i386 "-march=pentium")
+    set(CFLAGS_armv7 -target thumbv7-apple-darwin-eabi)
+    set(CFLAGS_i386 -march=pentium)
 
     darwin_read_list_from_file(common_FUNCTIONS ${MACHO_SYM_DIR}/common.txt)
     darwin_read_list_from_file(thumb2_FUNCTIONS ${MACHO_SYM_DIR}/thumb2.txt)
diff --git a/compiler-rt/cmake/Modules/CompilerRTUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
--- a/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
+++ b/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
@@ -5,19 +5,11 @@
 # define a handy helper function for it. The compile flags setting in CMake
 # has serious issues that make its syntax challenging at best.
 function(set_target_compile_flags target)
-  set(argstring "")
-  foreach(arg ${ARGN})
-    set(argstring "${argstring} ${arg}")
-  endforeach()
-  set_property(TARGET ${target} PROPERTY COMPILE_FLAGS "${argstring}")
+  set_property(TARGET ${target} PROPERTY COMPILE_OPTIONS ${ARGN})
 endfunction()
 
 function(set_target_link_flags target)
-  set(argstring "")
-  foreach(arg ${ARGN})
-    set(argstring "${argstring} ${arg}")
-  endforeach()
-  set_property(TARGET ${target} PROPERTY LINK_FLAGS "${argstring}")
+  set_property(TARGET ${target} PROPERTY LINK_OPTIONS ${ARGN})
 endfunction()
 
 # Set the variable var_PYBOOL to True if var holds a true-ish string,