Tools/Fsp: Replace PYTHON_HOME with sys.executable

Currently script Python interpreter is inconsistent with the
interpreter specified by Python home. This patch is to change
pythonhome to sys.executable.

Signed-off-by:  MingYue Liang <mingyuex.liang@intel.com>
Cc: Yuwei Chen <yuwei.chen@intel.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>

MinPlatformPkg/Tools/Fsp/RebaseAndPatchFspBinBaseAddress.py

@@ -73,9 +73,7 @@ file.close()
 # Get FSP-M Size, in order to calculate the FSP-T Base. Used SplitFspBin.py script 
 # to dump the header, and get the ImageSize in FSP-M section
 #
-pythontool = 'python'
-if 'PYTHON_HOME' in os.environ:
-    pythontool = os.environ['PYTHON_HOME'] + os.sep + 'python'
+pythontool = sys.executable
 Process = subprocess.Popen([pythontool, splitFspBinPath, "info","-f",fspBinFilePath], stdout=subprocess.PIPE)
 Output = Process.communicate()[0]
 FsptInfo = Output.rsplit(b"FSP_M", 1);