Remove gmp dependency and doc mentions

depends/packages/gmp.mk

@@ -1,30 +0,0 @@
-package=gmp
-$(package)_version=6.0.0a
-$(package)_download_path=https://gmplib.org/download/gmp
-$(package)_file_name=$(package)-$($(package)_version).tar.bz2
-$(package)_sha256_hash=7f8e9a804b9c6d07164cf754207be838ece1219425d64e28cfa3e70d5c759aaf
-$(package)_patches=arm_gmp_build_fix.patch darwin_gmp_build_fix.patch
-
-define $(package)_preprocess_cmds
-  patch -p1 < $($(package)_patch_dir)/arm_gmp_build_fix.patch && \
-  patch -p1 < $($(package)_patch_dir)/darwin_gmp_build_fix.patch
-endef
-
-define $(package)_set_vars
-  $(package)_config_opts=--disable-shared CC_FOR_BUILD=$(build_CC)
-  $(package)_config_opts_x86_64_darwin=--with-pic
-  $(package)_config_opts_x86_64_linux=--with-pic
-  $(package)_config_opts_arm_linux=--with-pic
-endef
-
-define $(package)_config_cmds
-  $($(package)_autoconf)
-endef
-
-define $(package)_build_cmds
-  $(MAKE)
-endef
-
-define $(package)_stage_cmds
-  $(MAKE) DESTDIR=$($(package)_staging_dir) install
-endef

depends/packages/packages.mk

@@ -1,4 +1,4 @@
-packages:=boost openssl gmp
+packages:=boost openssl
 native_packages := native_ccache native_comparisontool
 
 qt_native_packages = native_protobuf