[Patch V2] BaseTool: Fixed incremental rebuild issue.

["Feng, Bob C" <bob.c.feng@intel.com>]

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1540

This issue in introduced by commit
d943b0c339fe3d35ffdf9f580ccb7a55915c6854

To convert bytes to string, we need to use bytes.decode()
instead of using str(bytes). 

If the source file is not a txt file, ignore that file. 

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
---
 BaseTools/Source/Python/AutoGen/GenMake.py      | 16 ++++++++--------
 .../Source/Python/Workspace/DscBuildData.py     | 17 ++++++++---------
 2 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/BaseTools/Source/Python/AutoGen/GenMake.py b/BaseTools/Source/Python/AutoGen/GenMake.py
index 53c5b8577d..b441817b52 100644
--- a/BaseTools/Source/Python/AutoGen/GenMake.py
+++ b/BaseTools/Source/Python/AutoGen/GenMake.py
@@ -1043,18 +1043,18 @@ cleanlib:
                     Fd.close()
                 except BaseException as X:
                     EdkLogger.error("build", FILE_OPEN_FAILURE, ExtraData=F.Path + "\n\t" + str(X))
                 if len(FileContent) == 0:
                     continue
-
-                if FileContent[0] == 0xff or FileContent[0] == 0xfe:
-                    FileContent = FileContent.decode('utf-16')
-                else:
-                    try:
-                        FileContent = str(FileContent)
-                    except:
-                        pass
+                try:
+                    if FileContent[0] == 0xff or FileContent[0] == 0xfe:
+                        FileContent = FileContent.decode('utf-16')
+                    else:
+                        FileContent = FileContent.decode()
+                except:
+                    # The file is not txt file. for example .mcb file
+                    continue
                 IncludedFileList = gIncludePattern.findall(FileContent)
 
                 for Inc in IncludedFileList:
                     Inc = Inc.strip()
                     # if there's macro used to reference header file, expand it
diff --git a/BaseTools/Source/Python/Workspace/DscBuildData.py b/BaseTools/Source/Python/Workspace/DscBuildData.py
index 1ffefe6e7e..7221946062 100644
--- a/BaseTools/Source/Python/Workspace/DscBuildData.py
+++ b/BaseTools/Source/Python/Workspace/DscBuildData.py
@@ -153,19 +153,18 @@ def GetDependencyList(FileStack, SearchPathList):
                     Fd.close()
 
             if len(FileContent) == 0:
                 continue
 
-            if FileContent[0] == 0xff or FileContent[0] == 0xfe:
-                FileContent = FileContent.decode('utf-16')
-                IncludedFileList = gIncludePattern.findall(FileContent)
-            else:
-                try:
-                    FileContent = str(FileContent)
-                    IncludedFileList = gIncludePattern.findall(FileContent)
-                except:
-                    pass
+            try:
+                if FileContent[0] == 0xff or FileContent[0] == 0xfe:
+                    FileContent = FileContent.decode('utf-16')
+                else:
+                    FileContent = FileContent.decode()
+            except:
+                # The file is not txt file. for example .mcb file
+                continue
             IncludedFileList = gIncludePattern.findall(FileContent)
 
             for Inc in IncludedFileList:
                 Inc = Inc.strip()
                 Inc = os.path.normpath(Inc)
-- 
2.18.0.windows.1