Why is the check for installed tools failing on Windows when I try to build Wireshark?

Hi I am trying to compile the wireshark source code with the newly placed wpcap.dll and packet.dll which was compiled by me with some changes.while i am going through step by step guide of compiling i am getting following error while verifying the tools.All the tools are installed correctly according to my knowledge.Can any one help me in solving these errors.

C:\Development\wireshark-1.99.6>nmake -f makefile.nmake verify_tools
Microsoft (R) Program Maintenance Utility Version 12.00.21005.1
Copyright (C) Microsoft Corporation.  All rights reserved.
ERROR: The contents of 'C:\Development\Wireshark-win32-libs\current_tag.txt' is
(unknown).
It should be 2015-04-06.
Checking for required applications:
cl: /cygdrive/c/Program Files/Microsoft Visual Studio 12.0/VC/BIN/cl
link: /cygdrive/c/Program Files/Microsoft Visual Studio 12.0/VC/BIN/link
nmake: /cygdrive/c/Program Files/Microsoft Visual Studio 12.0/VC/BIN/nmake
bash: /usr/bin/bash
env: /usr/bin/env
grep: /usr/bin/grep
/usr/bin/find: /usr/bin/find
peflags: /usr/bin/peflags
C:\tools\python2\python.exe: /cygdrive/c/tools/python2/python.exe
C:\Qt\5.4\msvc2013\bin\qmake: /cygdrive/c/Qt/5.4/msvc2013/bin/qmake
sed: /usr/bin/sed
wget: /cygdrive/c/ProgramData/chocolatey/bin/wget
Can't find:  perl unzip
ERROR: These application(s) are either not installed or simply can't be found in the current PATH: /cygdrive/c/tools/python2:/cygdrive/c/Program Files/Microsoft Visual Studio 12.0/Common7/IDE/CommonExtensions/Microsoft/TestWindow:/cygdrive/c/Program Files/Microsoft SDKs/F#/3.1/Framework/v4.0:/cygdrive/c/Program Files/MSBuild/12.0/bin:/cygdrive/c/Program Files/Microsoft Visual Studio 12.0/Common7/IDE:/cygdrive/c/Program Files/Microsoft Visual Studio 12.0/VC/BIN:/cygdrive/c/Program Files/Microsoft Visual Studio 12.0/Common7/Tools:/cygdrive/c/Windows/Microsoft.NET/Framework/v4.0.30319:/cygdrive/c/Program Files/Microsoft Visual Studio 12.0/VC/VCPackages:/cygdrive/c/Program Files/HTML Help Workshop:/cygdrive/c/Program Files/Microsoft Visual Studio 12.0/Team Tools/Performance Tools:/cygdrive/c/Program Files/Windows Kits/8.1/bin/x86:/cygdrive/c/Program Files/Microsoft SDKs/Windows/v8.1A/bin/NETFX 4.5.1 Tools:/cygdrive/c/Windows/system32:/cygdrive/c/Windows:/cygdrive/c/Windows/System32/Wbem:/cygdrive/c/Windows/System32/WindowsPowerShell/v1.0:/cygdrive/c/Program Files/Windows Kits/8.1/Windows Performance Toolkit:/cygdrive/c/Program Files/Microsoft SQL Server/110/Tools/Binn:/cygdrive/c/Program Files/Microsoft SDKs/TypeScript/1.0:/cygdrive/c/Program Files/Microsoft SQL Server/120/Tools/Binn:/cygdrive/c/tools/python2:/cygdrive/c/Program Files/Microsoft SQL Server/90/Tools/binn:/cygdrive/c/ProgramData/chocolatey/bin:/cygdrive/c/tools/cygwin:/cygdrive/c/Program Files/HTML Help Workshop:/usr/bin:/cygdrive/c/Development/Wireshark-win32-libs/gtk2/bin:/cygdrive/c/bin:/cygdrive/c/Development/Wireshark-win32-libs/zlib-1.2.8.
For additional help, please visit:
http://www.wireshark.org/docs/wsdg_html_chunked/ChSetupWin32.html
NMAKE : fatal error U1077: 'C:\cygwin\bin\bash.EXE' : return code '0x1'
Stop.

Thanks, Karun