use cacheable zip snapshot instead of cloning mingw

- had some reliability issues with sourceforge's git mirror

Author: MartinNowak

create_dmd_release/build_all.d

@@ -460,6 +460,8 @@ int main(string[] args)
     enum libC = "snn.lib";
     enum libCurl = "libcurl-7.52.1-WinSSL-zlib-x86-x64.zip";
     enum omflibs = "omflibs-winsdk-10.0.16299.15.zip";
+    // 5.0-active branch
+    enum mingw_wsl = "mingw-mingw-org-wsl-a771e066eaf830a3a94a21968939748e8af776d2.zip";
 
     auto oldCompilers = platforms
         .map!(p => "dmd.%1$s.%2$s.%3$s".format(oldVer, p, p.os == OS.windows ? "7z" : "tar.xz"));
@@ -470,6 +472,7 @@ int main(string[] args)
     fetchFile("http://ftp.digitalmars.com/"~libC, cacheDir~"/"~libC);
     fetchFile("http://downloads.dlang.org/other/"~libCurl, cacheDir~"/"~libCurl, true);
     fetchFile("http://downloads.dlang.org/other/"~omflibs, cacheDir~"/"~omflibs, true);
+    fetchFile("https://sourceforge.net/code-snapshots/git/m/mi/mingw/mingw-org-wsl.git/"~mingw_wsl, cacheDir~"/"~mingw_wsl);
 
     // Unpack previous dmd release
     foreach (platform, oldCompiler; platforms.zip(oldCompilers))
@@ -487,9 +490,9 @@ int main(string[] args)
         extract(cacheDir~"/"~libCurl, workDir~"/windows/old-dmd/");
         // Get updated OMF import libraries
         extract(cacheDir~"/"~omflibs, workDir~"/windows/old-dmd/dmd2/windows/lib/");
-
-        // grab mingw sources
-        run("git clone --depth 1 --branch 5.0-active https://git.code.sf.net/p/mingw/mingw-org-wsl.git " ~ workDir ~ "/clones/mingw");
+        // Get mingw sources
+        extract(cacheDir~"/"~mingw_wsl, workDir~"/clones");
+        run("mv %s %s".format(workDir~"/clones/"~mingw_wsl.stripExtension, workDir~"/clones/mingw"));
     }
 
     cloneSources(gitTag, dubTag, isBranch, skipDocs, workDir~"/clones");