ovmf: fix gcc12 warning in LzmaEnc

Backport [https://github.com/tianocore/edk2/commit/85021f8cf22d1bd4114803c6c610dea5ef0059f1

]

Fixes:

Sdk/C/LzmaEnc.c: In function ?LzmaEnc_CodeOneMemBlock?:
Sdk/C/LzmaEnc.c:2828:19: error: storing the address of local variable ?outStream? in ?*p.rc.outStream? [-Werror=dangling-pointer=]
 2828 |   p->rc.outStream = &outStream.vt;
      |   ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
Sdk/C/LzmaEnc.c:2811:28: note: ?outStream? declared here
 2811 |   CLzmaEnc_SeqOutStreamBuf outStream;
      |                            ^~~~~~~~~
Sdk/C/LzmaEnc.c:2811:28: note: ?pp? declared here
Sdk/C/LzmaEnc.c:2828:19: error: storing the address of local variable ?outStream? in ?*(CLzmaEnc *)pp.rc.outStream? [-Werror=dangling-pointer=]
 2828 |   p->rc.outStream = &outStream.vt;
      |   ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
Sdk/C/LzmaEnc.c:2811:28: note: ?outStream? declared here
 2811 |   CLzmaEnc_SeqOutStreamBuf outStream;
      |                            ^~~~~~~~~
Sdk/C/LzmaEnc.c:2811:28: note: ?pp? declared here
cc1: all warnings being treated as errors

Signed-off-by: Steve Sakoman <steve@sakoman.com>