BaseTools:fix issue for decode the stdout/stderr byte arrays

BaseTools:fix issue for decode the stdout/stderr byte arrays

BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=2365

This patch is to fix a build tool regression issue which was introduced
by commit 8ddec24dea74.

compiler output message includes localized string.
So build failed when code decode the stdout/stderr byte arrays.
The cause of the build failed is that Commit 8ddec24dea74
removed "errors='ignore'".

The build tool does not need to deal with localized string,
so we need to add "errors='ignore'".

this function is only invoked for structure PCDs.
Build failed if structurePcd is used in platform dsc file.
The patch is going to fixed this issue

Cc: Liming Gao <liming.gao@intel.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>