[gn build] port b2a162e63b (liblldb.dll)

This requires making liblldb a dll on Windows.
Things still work with a static lib on non-Windows, so keep it a
static lib there for now.

llvm/utils/gn/secondary/lldb/source/API/BUILD.gn

@@ -1,6 +1,16 @@
-static_library("liblldb") {
-  # XXX if win -DEXPORT_LIBLLDB
+# The LLDB_IN_LIBLLDB setup requires that liblldb is a shared_library
+# on Windows.
+# FIXME: Consider making it a shared_library everywhere like in cmake?
+# (Having it a static_library is simpler -- no need for
+# -Wl,-runpath=$ORIGIN/../lib in executables on unix or the corresponding @loader_path on mac,
+# no need for .exports files, etc.)
+if (current_os == "win") {
+  liblldb_type = "shared_library"
+} else {
+  liblldb_type = "static_library"
+}
 
+target(liblldb_type, "liblldb") {
   # XXX LLDB_BUILD_FRAMEWORK
   # XXX LLDB_ENABLE_PYTHON
   # XXX LLDB_ENABLE_LUA
@@ -100,6 +110,10 @@ static_library("liblldb") {
     "SystemInitializerFull.cpp",
   ]
 
+  if (current_os == "win") {
+    defines = [ "LLDB_IN_LIBLLDB" ]
+  }
+
   # XXX liblldb.exports or liblldb-private.expoorts
   # XXX dep on clang resource directory
 }

llvm/utils/gn/secondary/lldb/tools/driver/BUILD.gn

@@ -47,6 +47,5 @@ executable("lldb") {
     "Platform.cpp",
   ]
 
-  # XXX if win -DIMPORT_LIBLLDB
   # XXX LLDB_BUILD_FRAMEWORK rpath stuff
 }