Fixed build (#1038)

* Changed libgmp url to our mirror
The original failing source at gmplib.org admits to blocking the DoS-like number of requests for dependencies on their server. This is a reasonable action for us to relieve reliance on a third-party server.

* Fixed url

* Added zlib and qt download mirrors
Presuming that these popular dependencies are in the same boat.

depends/packages/gmp.mk

@@ -1,6 +1,6 @@
 package=gmp
 $(package)_version=6.1.2
-$(package)_download_path=https://gmplib.org/download/gmp
+$(package)_download_path=https://mirror-eu1.veil.tools/packages/libgmp
 $(package)_file_name=$(package)-$($(package)_version).tar.bz2
 $(package)_sha256_hash=5275bb04f4863a13516b2f39392ac5e272f5e1bb8057b18aec1c9b79d73d8fb2
 

depends/packages/qt.mk

@@ -1,6 +1,6 @@
 PACKAGE=qt
 $(package)_version=5.9.8
-$(package)_download_path=https://download.qt.io/official_releases/qt/5.9/$($(package)_version)/submodules
+$(package)_download_path=https://mirror-eu1.veil.tools/packages/qt
 $(package)_suffix=opensource-src-$($(package)_version).tar.xz
 $(package)_file_name=qtbase-$($(package)_suffix)
 $(package)_sha256_hash=9b9dec1f67df1f94bce2955c5604de992d529dde72050239154c56352da0907d

depends/packages/zlib.mk

@@ -1,6 +1,6 @@
 package=zlib
 $(package)_version=1.2.11
-$(package)_download_path=http://www.zlib.net
+$(package)_download_path=https://mirror-eu1.veil.tools/packages/zlib
 $(package)_file_name=$(package)-$($(package)_version).tar.gz
 $(package)_sha256_hash=c3e5e9fdd5004dcb542feda5ee4f0ff0744628baf8ed2dd5d66f8ca1197cb1a1