diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index 3d77573661674..bafc111dd3104 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -57,9 +57,14 @@ if(LLVM_LIBC_FULL_BUILD OR LIBC_GPU_BUILD OR LIBC_GPU_ARCHITECTURES)
   endif()
 endif()
 
+foreach(name default ${LLVM_RUNTIME_TARGETS} ${LLVM_EXTRA_RUNTIME_TARGETS})
+  if("libc" IN_LIST LLVM_ENABLE_RUNTIMES OR "libc" IN_LIST RUNTIMES_${name}_LLVM_ENABLE_RUNTIMES)
+    set(LIBC_RUNTIMES_BUILD ON)
+  endif()
+endforeach()
+
 option(LIBC_HDRGEN_ONLY "Only build the 'libc-hdrgen' executable" OFF)
-if(("libc" IN_LIST LLVM_ENABLE_RUNTIMES AND NOT LLVM_RUNTIMES_BUILD) OR 
-   LIBC_HDRGEN_ONLY)
+if((LIBC_RUNTIMES_BUILD AND NOT LLVM_RUNTIMES_BUILD) OR LIBC_HDRGEN_ONLY)
   # When libc is build as part of the runtimes/bootstrap build's CMake run, we
   # only need to build the host tools to build the libc. So, we just do enough
   # to build libc-hdrgen and return.
diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 98cef005f07e0..f57228eb0f2c8 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -168,15 +168,17 @@ foreach(proj IN LISTS LLVM_ENABLE_RUNTIMES)
   endif()
 endforeach()
 
-if ("libc" IN_LIST LLVM_ENABLE_RUNTIMES)
-  # To build the libc runtime, we need to be able to build few libc build
-  # tools from the "libc" project. So, we add it to the list of enabled
-  # projects.
-  if (NOT "libc" IN_LIST LLVM_ENABLE_PROJECTS)
-    message(STATUS "Enabling libc project to build libc build tools")
-    list(APPEND LLVM_ENABLE_PROJECTS "libc")
+foreach(name default ${LLVM_RUNTIME_TARGETS} ${LLVM_EXTRA_RUNTIME_TARGETS})
+  if("libc" IN_LIST LLVM_ENABLE_RUNTIMES OR "libc" IN_LIST RUNTIMES_${name}_LLVM_ENABLE_RUNTIMES)
+    # To build the libc runtime, we need to be able to build few libc build
+    # tools from the "libc" project. So, we add it to the list of enabled
+    # projects.
+    if(NOT "libc" IN_LIST LLVM_ENABLE_PROJECTS)
+      message(STATUS "Enabling libc project to build libc build tools")
+      list(APPEND LLVM_ENABLE_PROJECTS "libc")
+    endif()
   endif()
-endif()
+endforeach()
 
 # LLVM_ENABLE_PROJECTS_USED is `ON` if the user has ever used the
 # `LLVM_ENABLE_PROJECTS` CMake cache variable.  This exists for
diff --git a/llvm/runtimes/CMakeLists.txt b/llvm/runtimes/CMakeLists.txt
index 8c48d85a4346f..035849020f990 100644
--- a/llvm/runtimes/CMakeLists.txt
+++ b/llvm/runtimes/CMakeLists.txt
@@ -449,14 +449,14 @@ if(runtimes)
       endforeach()
     endif()
   endif()
-  if(NOT LLVM_RUNTIME_TARGETS)
+  if(NOT LLVM_RUNTIME_TARGETS AND NOT LLVM_EXTRA_RUNTIME_TARGETS)
     runtime_default_target(
       DEPENDS ${builtins_dep} ${extra_deps}
       CMAKE_ARGS ${libc_cmake_args}
       PREFIXES ${prefixes})
     set(test_targets check-runtimes)
   else()
-    if("default" IN_LIST LLVM_RUNTIME_TARGETS)
+    if("default" IN_LIST LLVM_RUNTIME_TARGETS OR LLVM_EXTRA_RUNTIME_TARGETS)
       runtime_default_target(
         DEPENDS ${builtins_dep} ${extra_deps}
         CMAKE_ARGS ${libc_cmake_args}
@@ -481,7 +481,7 @@ if(runtimes)
       endif()
     endif()
 
-    foreach(name ${LLVM_RUNTIME_TARGETS})
+    foreach(name ${LLVM_RUNTIME_TARGETS} ${LLVM_EXTRA_RUNTIME_TARGETS})
       if(builtins_dep)
         if (LLVM_BUILTIN_TARGETS)
           set(builtins_dep_name "${builtins_dep}-${name}")