1 files changed, 5 insertions, 0 deletions
diff --git a/BaseTools/Source/Python/build/build.py b/BaseTools/Source/Python/build/build.py
index 1e14fb4dcc..eff1e66b08 100644
--- a/BaseTools/Source/Python/build/build.py
+++ b/BaseTools/Source/Python/build/build.py
@@ -1029,6 +1029,11 @@ class Build():
         if self.Prebuild:
             EdkLogger.info("\n- Prebuild Start -\n")
             self.LaunchPrebuildFlag = True
+            #
+            # The purpose of .PrebuildEnv file is capture environment variable settings set by the prebuild script
+            # and preserve them for the rest of the main build step, because the child process environment will
+            # evaporate as soon as it exits, we cannot get it in build step.
+            #
             PrebuildEnvFile = os.path.join(GlobalData.gConfDirectory,'.cache','.PrebuildEnv')
             if os.path.isfile(PrebuildEnvFile):
                 os.remove(PrebuildEnvFile)