The layouts of resilient value types shipped in the Swift 5 standard library
x and overlays will forever be frozen in time for backward deployment to old
Objective-C runtimes. This PR ensures that even if the layouts of these types
evolve in the future, binaries built to run on the old runtime will continue
to lay out class instances in a manner compatible with Swift 5.
Fixes <rdar://problem/45646886>.
This converts the instances of the pattern for which we have a proper
substitution in lit. This will make it easier to replace it
appropriately with Windows equivalents.
Fixed for the difference of Cygwin with other Windows variants (MSVC,
Itanium, MinGW).
- The platform name is renamed to "cygwin" from "windows" which is used
for searching the standard libraries.
- The consideration for DLL storage class (DllExport/DllImport) is not
required for Cygwin and MinGW. There is no problem when linking in
these environment.
- Cygwin should use large memory model as default.(This may be changed
if someone ports to 32bit)
- Cygwin and MinGW should use the autolink feature in the sameway of
Linux due to the linker's limit.
