Revert "src.opts.mk: Enable LLDB by default globally"

This breaks the riscv64 build; clearly the version we have in-tree is
not new enough to work. That or our build system needs tweaking. Either
way, we're not ready for this, and enabling it without testing was
misguided.

This reverts commit c59a47dc6c.

share/mk/src.opts.mk

@@ -124,7 +124,6 @@ __DEFAULT_YES_OPTIONS = \
     LEGACY_CONSOLE \
     LLD \
     LLD_BOOTSTRAP \
-    LLDB \
     LLVM_ASSERTIONS \
     LLVM_BINUTILS \
     LLVM_COV \
@@ -306,6 +305,11 @@ __DEFAULT_NO_OPTIONS+=FDT
 __DEFAULT_YES_OPTIONS+=FDT
 .endif
 
+.if ${__T:Mriscv64*} == ""
+__DEFAULT_YES_OPTIONS+=LLDB
+.else
+__DEFAULT_NO_OPTIONS+=LLDB
+.endif
 # LIB32 is not supported on all 64-bit architectures.
 .if (${__T:Maarch64*} != "" && ((defined(X_COMPILER_TYPE) && ${X_COMPILER_TYPE} != "gcc") || (!defined(X_COMPILER_TYPE) && ${COMPILER_TYPE} != "gcc"))) || ${__T} == "amd64" || ${__T} == "powerpc64"
 __DEFAULT_YES_OPTIONS+=LIB32