procedure MapArchiveExtensions(const DestExt, SourceExt: String);
Allows files with a specified destination extension, such as .exe, to be treated as if they have a different source extension, such as .7z, for extraction purposes.
An exception will be raised if there was an error.
Calls to this function are ignored if the ArchiveExtraction [Setup] section directive is set to basic. In this case files as always extracted as .7z, regardless of the extension.
[Files]
Source: "{src}\My7ZipSFX.exe; DestDir: "{app}"; Flags: external extractarchive recursesubdirs createallsubdirs ignoreversion
[Code]
function InitializeSetup: Boolean;
begin
MapArchiveExtensions('.exe', '.7z');
end;