Merge bitcoin/bitcoin#22410: Avoid GCC 7.1 ABI change warning in guix build

1edddf5 Avoid GCC 7.1 ABI change warning in guix build (Pieter Wuille)

Pull request description:

  The arm-linux-gnueabihf guix build output is littered with warnings like:

  ```
  /gnu/store/7a96hdqdb2qi8a39f09n84xjy2hr23rs-gcc-cross-arm-linux-gnueabihf-8.4.0/include/c++/bits/stl_vector.h:1085:4: note:
                   parameter passing for argument of type '__gnu_cxx::__normal_iterator<CRecipient*, std::vector<CRecipient> >' changed in GCC 7.1
  ```

  These are irrelevant for us. Disable them using `-Wno-psabi`.

ACKs for top commit:
  laanwj:
    ACK 1edddf5
  hebasto:
    ACK 1edddf5, after thorough reading related materials, I agree this change can be merged. As I mentioned above, I have been compiling my arm-32bit binaries with `-Wno-psabi` flag for two years, and no related flaws were observed.

Tree-SHA512: 485c7500547ac5da567ad23847341c18ff832607f5a1002676404cc647e437cf3445b6894ecff5b52929ca52bea946c06bd90eace1997c895e56204e787065e4

Author: fanquake

contrib/guix/libexec/build.sh

@@ -254,6 +254,10 @@ esac
 # CXXFLAGS
 HOST_CXXFLAGS="$HOST_CFLAGS"
 
+case "$HOST" in
+    arm-linux-gnueabihf) HOST_CXXFLAGS="${HOST_CXXFLAGS} -Wno-psabi" ;;
+esac
+
 # LDFLAGS
 case "$HOST" in
     *linux*)  HOST_LDFLAGS="-Wl,--as-needed -Wl,--dynamic-linker=$glibc_dynamic_linker -static-libstdc++ -Wl,-O2" ;;