[LLDB] Simplify cmake for instruction emulation unit tests

[DavidSpickett]

Summary

I got suspicious because of checking "ARM" for an "ARM64" plugin.
As far as I can tell these never needed an llvm target to function.

Looking at the corresponding cmake for the libraries under test they
don't reference target libraries either.

[labath]

If the tests work without the corresponding llvm targets, then yea, ship it.

lldb/unittests/Instruction/CMakeLists.txt

-set(FILES "")
-set(DEPS "")
-
-if ("ARM" IN_LIST LLVM_TARGETS_TO_BUILD)
-  list(APPEND FILES ARM64/TestAArch64Emulator.cpp)
-  list(APPEND DEPS lldbPluginInstructionARM64)
-endif ()
-
-if ("RISCV" IN_LIST LLVM_TARGETS_TO_BUILD)
-  list(APPEND FILES RISCV/TestRISCVEmulator.cpp)
-  list(APPEND DEPS lldbPluginInstructionRISCV)
-endif ()
-
-list(LENGTH FILES LISTLEN)
-
-if (LISTLEN GREATER 0)
-  add_lldb_unittest(EmulatorTests
-    ${FILES}
+  ARM64/TestAArch64Emulator.cpp
+  RISCV/TestRISCVEmulator.cpp
 
-    LINK_LIBS
-      lldbCore
-      lldbSymbol
-      lldbTarget
-      ${DEPS}
-    LINK_COMPONENTS
-      Support
-      ${LLVM_TARGETS_TO_BUILD}
-    )
-endif ()
+    lldbPluginInstructionARM64
+    lldbPluginInstructionRISCV
+
+  )