--- a/compiler-rt/cmake/config-ix.cmake.ORIG	2021-01-29 09:54:20.880593534 +0100
+++ b/compiler-rt/cmake/config-ix.cmake	2021-01-29 09:58:49.595603555 +0100
@@ -444,10 +444,7 @@
     ${DARWIN_COMMON_LINK_FLAGS}
     ${DARWIN_osx_MIN_VER_FLAG}=${SANITIZER_MIN_OSX_VERSION})
 
-  if(DARWIN_osx_SYSROOT)
-    list(APPEND DARWIN_osx_CFLAGS -isysroot ${DARWIN_osx_SYSROOT})
-    list(APPEND DARWIN_osx_LINK_FLAGS -isysroot ${DARWIN_osx_SYSROOT})
-  endif()
+  # Do not add -isysroot flag on Gentoo Prefix (search paths handled by cmake)
 
   # Figure out which arches to use for each OS
   darwin_get_toolchain_supported_archs(toolchain_arches)
--- a/compiler-rt/cmake/base-config-ix.cmakeORIG	2021-01-29 09:54:20.880593534 +0100
+++ b/compiler-rt/cmake/base-config-ix.cmake	2021-01-29 09:59:41.087605475 +0100
@@ -101,23 +101,8 @@
 endif()
 
 if(APPLE)
-  # On Darwin if /usr/include/c++ doesn't exist, the user probably has Xcode but
-  # not the command line tools (or is using macOS 10.14 or newer). If this is
-  # the case, we need to find the OS X sysroot to pass to clang.
-  if(NOT EXISTS /usr/include/c++)
-    execute_process(COMMAND xcrun -sdk macosx --show-sdk-path
-       OUTPUT_VARIABLE OSX_SYSROOT
-       ERROR_QUIET
-       OUTPUT_STRIP_TRAILING_WHITESPACE)
-    if (NOT OSX_SYSROOT OR NOT EXISTS ${OSX_SYSROOT})
-      message(WARNING "Detected OSX_SYSROOT ${OSX_SYSROOT} does not exist")
-    else()
-      message(STATUS "Found OSX_SYSROOT: ${OSX_SYSROOT}")
-      set(OSX_SYSROOT_FLAG "-isysroot${OSX_SYSROOT}")
-    endif()
-  else()
-    set(OSX_SYSROOT_FLAG "")
-  endif()
+  # Do not add -isysroot flag on Gentoo Prefix (search paths handled by cmake)
+  set(OSX_SYSROOT_FLAG "")
 
   option(COMPILER_RT_ENABLE_IOS "Enable building for iOS" On)
   option(COMPILER_RT_ENABLE_WATCHOS "Enable building for watchOS - Experimental" Off)
--- a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake.ORIG	2021-01-29 09:54:20.879593534 +0100
+++ b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake	2021-01-29 10:00:45.701607884 +0100
@@ -273,7 +273,8 @@
     ${ARGN})
   set(libname "${name}.${suffix}_${LIB_ARCH}_${LIB_OS}")
   add_library(${libname} STATIC ${LIB_SOURCES})
-  if(DARWIN_${LIB_OS}_SYSROOT)
+  # Do not add -isysroot flag on Gentoo Prefix (search paths handled by cmake)
+  if(DARWIN_${LIB_OS}_SYSROOT AND NOT "${LIB_OS}" STREQUAL "osx")
     set(sysroot_flag -isysroot ${DARWIN_${LIB_OS}_SYSROOT})
   endif()
 
--- a/compiler-rt/cmake/Modules/AddCompilerRT.cmake.ORIG	2021-01-29 09:54:20.879593534 +0100
+++ b/compiler-rt/cmake/Modules/AddCompilerRT.cmake	2021-01-29 10:01:40.267609919 +0100
@@ -278,7 +278,8 @@
       if(CMAKE_C_COMPILER_ID MATCHES Clang AND CMAKE_C_COMPILER_TARGET)
         list(APPEND extra_cflags_${libname} "--target=${CMAKE_C_COMPILER_TARGET}")
       endif()
-      if(CMAKE_SYSROOT)
+      # Do not add --sysroot flag on Gentoo Prefix (search paths handled by cmake)
+      if(CMAKE_SYSROOT AND NOT APPLE)
         list(APPEND extra_cflags_${libname} "--sysroot=${CMAKE_SYSROOT}")
       endif()
       string(REPLACE ";" " " extra_cflags_${libname} "${extra_cflags_${libname}}")