Comment # 1 on bug 1230425 from Joey Lee

After tracing edk2 code, I found that the _ASSERT macro used __FILE_NAME__ and
__FILE__ extension for getting the filename of source code:
MdePkg/Include/Library/DebugLib.h

  #if defined (_ASSERT)
    #undef _ASSERT
  #endif
  #if defined (__clang__) && defined (__FILE_NAME__)
#define _ASSERT(Expression)  UnitTestDebugAssert (__FILE_NAME__,
DEBUG_LINE_NUMBER, DEBUG_EXPRESSION_STRING (Expression))
  #else
#define _ASSERT(Expression)  UnitTestDebugAssert (__FILE__, DEBUG_LINE_NUMBER,
DEBUG_EXPRESSION_STRING (Expression))
  #endif
#else
  #if defined (__clang__) && defined (__FILE_NAME__)
#define _ASSERT(Expression)  DebugAssert (__FILE_NAME__, DEBUG_LINE_NUMBER,
DEBUG_EXPRESSION_STRING (Expression))  
  #else
#define _ASSERT(Expression)  DebugAssert (__FILE__, DEBUG_LINE_NUMBER,
DEBUG_EXPRESSION_STRING (Expression))       
  #endif
#endif

That's why pe32+ binary file has many build root folder name. And longer build
root name will produce bigger FV image.