BaseTools/Trim: Normalize filepaths to fix comparisons on Windows

BaseTools/Trim: Normalize filepaths to fix comparisons on Windows

When using Linaro GCC5+ arm-eabi toolchain on Windows, the generated
DSDT.iii contains a canonicalized ("\.\" removed and lower case)
filepath for the preprocessed DSDT.i file in the first line.
Trim.exe is called on DSDT.iii to generate DSDT.iiii, which does a
line for line comparison of filepaths encountered to the preprocessed
DSDT.i filepath found in the first line to determine what lines to
place in DSDT.iiii. Since the DSDT.i filepath is canonicalized and
all later filepaths in DSDT.iii are not canonicalized, all comparisons
fail and the result is in an empty DSDT.iiii.

Issue was first reported to Linaro here:
https://bugs.linaro.org/show_bug.cgi?id=2909
where the recommendation was to address the issue in Trim.exe.

This patch normalizes the case and pathname of all filepaths
encountered during Trim.exe execution on preprocessed files.  This
fixes comparisons of filepaths that contain mismatching case on
case-insensitive filesystems, redundant separators, and uplevel
references.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Christopher Co <christopher.co@microsoft.com>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>