dist: fix reproducible build from release tarball

Make it possible to rebuild an identical copy from a release tarball. It
was previously only possible from a checked out git repository.

- add release-tools.sh to dist
- keep Makefile.dist around to include it in dist
- regenerate tool_huge.c with the new version in dist
- fix the dist CI job to not do make clean like before

Closes #14336

scripts/Makefile.am

@@ -24,7 +24,7 @@
 
 EXTRA_DIST = coverage.sh completion.pl firefox-db2pem.sh checksrc.pl    \
  mk-ca-bundle.pl schemetable.c cd2nroff nroff2cd cdall cd2cd managen \
- dmaketgz
+ dmaketgz release-tools.sh
 
 ZSH_FUNCTIONS_DIR = @ZSH_FUNCTIONS_DIR@
 FISH_FUNCTIONS_DIR = @FISH_FUNCTIONS_DIR@

scripts/managen

@@ -1205,14 +1205,20 @@ elsif($cmd eq "-c") {
 
 my @files = @ARGV; # the rest are the files
 
-open(INC, "<$include/curl/curlver.h");
-while(<INC>) {
-    if($_ =~ /^#define LIBCURL_VERSION \"([0-9.]*)/) {
-        $version = $1;
-        last;
-    }
+# can be overriden for releases
+if($ENV{'CURL_MAKETGZ_VERSION'}) {
+    $version = $ENV{'CURL_MAKETGZ_VERSION'};
+}
+else {
+    open(INC, "<$include/curl/curlver.h");
+    while(<INC>) {
+        if($_ =~ /^#define LIBCURL_VERSION \"([0-9.]*)/) {
+            $version = $1;
+            last;
+        }
+    }
+    close(INC);
 }
-close(INC);
 
 # learn all existing options
 indexoptions($dir, @files);