I think the problem is the type uuid_t is not defined at anywhere. So the declaration at line 662 in the file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/unistd.h will cause error for example.
In the first attempt, I tried to add one line into that unistd.h file:
#include <sys/_types/_uuid_t.h> at line 83. But it doesn't help.
Because I don't want to go deeper to edit many system file, I add another line into unistd.h to manually define the type of uuid_t, based on the definition in _uuid_t.h.
typedef __darwin_uuid_t uuid_t; at line 661, after "#endif".
Then it worked.
I am not sure if this is an error in the source code of MacOSX.10.15.sdk or not. But if you want to fix it in this way, please make sure you have the root permission when editing those files.