qemu: use a higher fallback value if sysctl vm.mmap_min_addr is not readable.

Issue https://github.com/termux/termux-packages/issues/6172.

packages/qemu-system-x86-64-headless/0013-mmap_min_addr-fallback.patch

@@ -0,0 +1,17 @@
+diff -uNr qemu-5.2.0/linux-user/main.c qemu-5.2.0.mod/linux-user/main.c
+--- qemu-5.2.0/linux-user/main.c	2020-12-08 18:59:44.000000000 +0200
++++ qemu-5.2.0.mod/linux-user/main.c	2020-12-24 17:41:07.982481916 +0200
+@@ -770,7 +770,13 @@
+      * If we're in a chroot with no /proc, fall back to 1 page.
+      */
+     if (mmap_min_addr == 0) {
++#ifdef __ANDROID__
++        // Go with 8 pages (32768 bytes) as default value for Android (Termux).
++        // Issue https://github.com/termux/termux-packages/issues/6172.
++        mmap_min_addr = qemu_host_page_size * 8;
++#else
+         mmap_min_addr = qemu_host_page_size;
++#endif
+         qemu_log_mask(CPU_LOG_PAGE,
+                       "host mmap_min_addr=0x%lx (fallback)\n",
+                       mmap_min_addr);

packages/qemu-system-x86-64-headless/build.sh

@@ -3,7 +3,7 @@ TERMUX_PKG_DESCRIPTION="A generic and open source machine emulator and virtualiz
 TERMUX_PKG_LICENSE="LGPL-2.1"
 TERMUX_PKG_MAINTAINER="Leonid Pliushch <leonid.pliushch@gmail.com>"
 TERMUX_PKG_VERSION=1:5.2.0
-TERMUX_PKG_REVISION=1
+TERMUX_PKG_REVISION=2
 TERMUX_PKG_SRCURL=https://download.qemu.org/qemu-${TERMUX_PKG_VERSION:2}.tar.xz
 TERMUX_PKG_SHA256="cb18d889b628fbe637672b0326789d9b0e3b8027e0445b936537c78549df17bc"
 TERMUX_PKG_DEPENDS="attr, glib, libbz2, libc++, libcap-ng, libcurl, libgcrypt, libiconv, libjpeg-turbo, liblzo, libnfs, libpixman, libpng, libssh, ncurses, qemu-common, resolv-conf, zlib"