VmgExitLib fails to build with the CLANG38 toolset (clang 13.0.0):

edk2/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c:1875:9: error: variable 'Compacted' is used uninitialized whenever 'if' condition is false [-Werror,-W
sometimes-uninitialized]
   if (EcxIn == 1) {
       ^~~~~~~~~~
edk2/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c:1895:12: note: uninitialized use occurs here
          Compacted
          ^~~~~~~~~
edk2/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c:1875:5: note: remove the 'if' if its condition is always true
   if (EcxIn == 1) {
   ^~~~~~~~~~~~~~~~
edk2/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c:1871:37: note: initialize the variable 'Compacted' to silence this warning
   BOOLEAN                Compacted;
                                   ^
                                    = '\0'

--
Rebecca Cran