BaseTools: Detect invalid library override (tianocore#452)

## Description

Ensures LIBRARY_CLASS as specified in the library override INF defines
section is the same value as the library class specified in the override
line.

## Example of mismatch
``` cmd
ERROR - EDK2 tianocore#2 from c:\src\mu_tiano_platforms\Platforms\QemuQ35Pkg\QemuQ35Pkg.dsc(...): LIBRARY_CLASS for override: [c:\src\mu_tiano_platforms\MU_BASECORE\MdePkg\Library\BasePcdLibNull\BasePcdLibNull.inf] does not match the library class being overridden: [DevicePathLib]
```

closes tianocore#314

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- [ ] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

Ensured mismatched library override was caught, and INF's with multiple
LIBRARY_CLASS definitions will not raise an error if one of the
definitions matches.

## Integration Instructions

N/A

BaseTools/Source/Python/Workspace/WorkspaceCommon.py

@@ -110,6 +110,26 @@ def GetModuleLibInstances(Module, Platform, BuildDatabase, Arch, Target, Toolcha
         if LibraryClass.startswith("NULL"):
             Module.LibraryClasses[LibraryClass] = Platform.Modules[str(Module)].LibraryClasses[LibraryClass]
 
+        # MU_CHANGE begin
+
+        # Compares the Library class being over written (var: LibraryClass) to the actual library class that is
+        # is doing the overridding.
+        # 
+        # i.e. ExampleLib|Path/To/ExampleLibBase.inf:
+        #     ensuring ExampleLib == LIBRARY_CLASS in the define section of ExampleLibBase.inf
+        else:
+            path = Platform.Modules[str(Module)].LibraryClasses[LibraryClass]
+            match = False
+            for LibraryClassObj in BuildDatabase[path, Arch, Target, Toolchain].LibraryClass:
+                if LibraryClass == LibraryClassObj.LibraryClass:
+                    match = True
+
+            if not match:
+                EdkLogger.error("build", BUILD_ERROR,
+                              "LIBRARY_CLASS for override: [%s] does not match the library class being overridden: [%s]" % (path, LibraryClass),
+                              File=FileName)
+        # MU_CHANGE end
+
     # EdkII module
     LibraryConsumerList = [Module]
     Constructor = []