glibc: update glibc to 2.26+ and switch to download from git

Switch glibc to 2.26+ [0] and download the sources from git which will it
make easier to update glibc in the future.

For an overview of the fixed bugs and CVE related fixes in 2.26+ see the
NEWS file [1]

[0] https://sourceware.org/git/?p=glibc.git;a=commit;h=d300041c533a3d837c9f37a099bcc95466860e98
[1] https://sourceware.org/git/?p=glibc.git;a=blob;f=NEWS;h=410f0d163145c1549fb73fdd96568f585b5bf62f;hb=refs/heads/release/2.26/master

Signed-off-by: Xinxing Hu <xinxing.huchn@gmail.com>
Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

toolchain/glibc/common.mk

@@ -9,11 +9,13 @@ include $(TOPDIR)/rules.mk
 PKG_NAME:=glibc
 PKG_VERSION:=2.26
 
-PKG_SOURCE_URL:=@GNU/libc
-PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
-PKG_HASH:=e54e0a934cd2bc94429be79da5e9385898d2306b9eaf3c92d5a77af96190f6bd
-
+PKG_SOURCE_PROTO:=git
 PKG_SOURCE_SUBDIR:=$(PKG_NAME)-$(PKG_VERSION)
+PKG_SOURCE_VERSION:=d300041c533a3d837c9f37a099bcc95466860e98
+PKG_MIRROR_HASH:=31e90926a1d3093355aa85c04c68b3d109c3dc3d9f80afe50505e864b32ac784
+PKG_SOURCE_URL:=git://sourceware.org/git/glibc.git
+PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION)-$(PKG_SOURCE_VERSION).tar.xz
+
 HOST_BUILD_DIR:=$(BUILD_DIR_TOOLCHAIN)/$(PKG_SOURCE_SUBDIR)
 CUR_BUILD_DIR:=$(HOST_BUILD_DIR)-$(VARIANT)
 PATCH_DIR:=$(PATH_PREFIX)/patches