depends: Support for S390X targets

depends/README.md

@@ -12,13 +12,13 @@ For example:
 
     make HOST=x86_64-w64-mingw32 -j4
 
-**Bitcoin's configure script by default will ignore the depends output.** In
+**Bitcoin Core's configure script by default will ignore the depends output.** In
 order for it to pick up libraries, tools, and settings from the depends build,
 you must point it at the appropriate `--prefix` directory generated by the
 build. In the above example, a prefix dir named x86_64-w64-mingw32 will be
 created. To use it for Bitcoin:
 
-    ./configure --prefix=`pwd`/depends/x86_64-w64-mingw32
+    ./configure --prefix=$PWD/depends/x86_64-w64-mingw32
 
 Common `host-platform-triplets` for cross compilation are:
 
@@ -32,6 +32,7 @@ Common `host-platform-triplets` for cross compilation are:
 - `powerpc64le-linux-gnu` for Linux POWER 64-bit (little endian)
 - `riscv32-linux-gnu` for Linux RISC-V 32 bit
 - `riscv64-linux-gnu` for Linux RISC-V 64 bit
+- `s390x-linux-gnu` for Linux S390X
 - `armv7a-linux-android` for Android ARM 32 bit
 - `aarch64-linux-android` for Android ARM 64 bit
 - `i686-linux-android` for Android x86 32 bit
@@ -74,6 +75,10 @@ For linux RISC-V 64-bit cross compilation (there are no packages for 32-bit):
 RISC-V known issue: gcc-7.3.0 and gcc-7.3.1 result in a broken `test_bitcoin` executable (see https://github.com/bitcoin/bitcoin/pull/13543),
 this is apparently fixed in gcc-8.1.0.
 
+For linux S390X cross compilation:
+
+    sudo apt-get install g++-s390x-linux-gnu binutils-s390x-linux-gnu
+
 ### Dependency Options
 The following can be set when running make: make FOO=bar