Correct shell escaping in 7zip command

Fixes #340

src/BinDeps.jl

@@ -113,12 +113,13 @@ if Compat.Sys.iswindows()
     const exe7z = joinpath(JULIA_HOME, "7z.exe")
 
     function unpack_cmd(file,directory,extension,secondary_extension)
-        if ((extension == ".Z" || extension == ".gz" || extension == ".xz" || extension == ".bz2") &&
-                secondary_extension == ".tar") || extension == ".tgz" || extension == ".tbz"
-            return pipeline(`$exe7z x $file -y -so`, `$exe7z x -si -y -ttar -o$directory`)
-        elseif (extension == ".zip" || extension == ".7z" || extension == ".tar" ||
-                (extension == ".exe" && secondary_extension == ".7z"))
-            return (`$exe7z x $file -y -o$directory`)
+        if (extension in [".Z", ".gz", ".xz", ".bz2"] && secondary_extension == ".tar") ||
+                extension == ".tgz" || extension == ".tbz"
+            return pipeline(Cmd([exe7z, "x", file, "-y", "-so"]),
+                            Cmd([exe7z, "x", "-si", "-y", "-ttar", "-o" * directory]))
+        elseif extension in [".zip", ".7z", ".tar"] ||
+                (extension == ".exe" && secondary_extension == ".7z")
+            return Cmd([exe7z, "x", file, "-y", "-o" * directory])
         end
         error("I don't know how to unpack $file")
     end

test/runtests.jl

@@ -33,3 +33,10 @@ let gv = glibc_version()
         @test gv === nothing
     end
 end
+
+if Compat.Sys.iswindows()
+    file = "C:\\junk.zip"
+    dir = "D:\\junk"
+    @test BinDeps.unpack_cmd(file, dir, ".zip", "") ==
+        `$(joinpath(JULIA_HOME, "7z.exe")) -x $file -y -o $dir`
+end