Execute script once before installing a directory tree - inno-setup

Question

I am trying to write an Inno Setup installer to install and then run other installers. The problem I have is when trying to install Cygwin. I have downloaded Cygwin and all packages I need so I can perform a local install. Then I want to add extra files and directories to the Cygwin installation.
My first attempt was like this:
[Files]
Source: "{#Cygwin}\Cygwin\*"; DestDir: {tmp}\cygwin; Flags: recursesubdirs;
Source: "{#Cygwin}\additional\*"; DestDir: {tmp}\cygwin\additional; Flags: recursesubdirs
[Run]
Filename: "{tmp}\cygwin\setup-x86_64.exe"; Parameters: "-q -L"; WorkingDir: "{tmp}";
But this means that I must have a script to add the additional files because there is nowhere to put them until Cygwin is actually installed by the command in the [Run] section.
I have tried using a BeforeInstall script in the [Files] section to run the Cygwin installer before adding the additional files, but because I have to use a wildcard with Source: "{#Cygwin}\additional\*"; the script is called once for every file in the directory tree.
The [Files] section of Inno Setup seems to only accept source files, and not a source directory, unless the directory has a wildcard.
Is there a way I can make it install everything from a directory tree without using a wildcard, or is there a way I can make the BeforeInstall script run just once, regardless of how many files are copied?

Answer 1

Install the Cygwin on the first call to BeforeInstall function only.
var
CygwinInstalled: Boolean;
procedure MyBeforeInstall;
begin
if CygwinInstalled then
begin
Log('Cygwin installed already');
end
else
begin
Log('Installing Cygwin');
{ install Cygwin here }
CygwinInstalled := true;
end;
end;