Support WINDOWS_EXPORT_ALL_SYMBOLS with `.def` files

The `WINDOWS_EXPORT_ALL_SYMBOLS` target property exports all symbols
found in object files explicitly given to the linker.  However, the
linker may also find additional symbols in dependencies and copy them
into the linked binary (e.g. from `msvcrt.lib`).  Provide a way to
export an explicit list of such symbols by adding a `.def` file as a
source file.

Fixes: #16473

1 files changed, 9 insertions, 0 deletions

diff --git a/Tests/ModuleDefinition/split_dll.c b/Tests/ModuleDefinition/split_dll.c
new file mode 100644
index 0000000..1546a2d
--- /dev/null
+++ b/Tests/ModuleDefinition/split_dll.c
@@ -0,0 +1,9 @@
+int split_dll_1(void)
+{
+  return 0;
+}
+
+int split_dll_2(void)
+{
+  return 0;
+}