[WebKit] fatal error U1077: 'bash' : '0x1'

When you happen to the problem, try putting your cygwin first in your Windows PATH.

For example:
C:\cygwin\bin;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;c:\Program Files\Microsoft SQL Server\90\Tools\binn\;


Reference:
http://ask.wireshark.org/questions/7991/nmake-fatal-error-u1077-sed-return-code-0x1