Revert "Remove external/lzma"

LZMA is needed for decompression of debug symbols in libunwind.
This reverts commit 8bc0273d91.
Change-Id: Id0622b56f6d682829a2bda6dd2a03e25fbb0fbee

default.xml

@@ -208,6 +208,7 @@
   <project path="external/lohit-fonts" name="platform/external/lohit-fonts" />
   <project path="external/ltrace" name="platform/external/ltrace" groups="pdk-cw-fs" />
   <project path="external/lz4" name="platform/external/lz4" groups="pdk-cw-fs" />
+  <project path="external/lzma" name="platform/external/lzma" groups="pdk" />
   <project path="external/markdown" name="platform/external/markdown" groups="pdk-cw-fs" />
   <project path="external/mdnsresponder" name="platform/external/mdnsresponder" groups="pdk" />
   <project path="external/mesa3d" name="platform/external/mesa3d" groups="pdk-cw-fs" />