swift-concurrency doesn't compile on linux

[LeoDog896]

(From stackotter/delta-client#113)

When compiling the repository mentioned above, when it reaches a subdependency of swift-concurrency, it reaches this error:

Working copy of https://github.com/apple/swift-log resolved at 1.4.2
'swift-nio-zlib-support': warning: ignoring declared target(s) 'swift-nio-zlib-support' in the system package
Building for production...
In file included from ./delta-client/.build/checkouts/JJLISO8601DateFormatter/Sources/JJLISO8601DateFormatter/JJLISO8601DateFormatter.m:3:
./delta-client/.build/checkouts/JJLISO8601DateFormatter/Sources/JJLISO8601DateFormatter/include/JJLISO8601DateFormatter.h:3:9: fatal error: 'Foundation/Foundation.h' file not found
#import <Foundation/Foundation.h>
        ^~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ./delta-client/.build/checkouts/swift-concurrency/Sources/ObjCBridges/AtomicBridges.m:17:
./delta-client/.build/checkouts/swift-concurrency/Sources/ObjCBridges/include/AtomicBridges.h:17:9: fatal error: 'Foundation/Foundation.h' file not found
#import <Foundation/Foundation.h>
        ^~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ./delta-client/.build/checkouts/JJLISO8601DateFormatter/Sources/JJLISO8601DateFormatter/JJLInternal.c:3:
1: error: unknown type name 'ssize_t'; did you mean 'size_t'?
ssize_t jjl_saferead(int fd, void *buffer, size_t nbytes);
^~~~~~~
size_t
'size_t' declared here
typedef __SIZE_TYPE__ size_t;
                      ^



1 error generated.
1 error generated.
[4/14] Compiling c-atomics.c