message: guix: Pin kernel header version
  Use 4.19 for riscv64 (earliest LTS release w/ riscv64 support)
  Use 4.9 for all others (second-oldest LTS release, released in
  combination with glibc glibc 2.24 in Debian stretch)
diff: @@ -156,7 +156,7 @@ chain for " target " development."))
  (define* (make-bitcoin-cross-toolchain target
  #:key
  (base-gcc-for-libc gcc-7)
  - (base-kernel-headers linux-libre-headers-5.4)
  + (base-kernel-headers linux-libre-headers-4.9)
  (base-libc (make-glibc-without-ssp glibc-2.24))
  (base-gcc (make-gcc-rpath-link base-gcc)))
  "Convenience wrapper around MAKE-CROSS-TOOLCHAIN with default values
  @@ -647,7 +647,9 @@ inspecting signatures in Mach-O binaries.")
  osslsigncode))
  ((string-contains target "-linux-")
  (list (cond ((string-contains target "riscv64-")
  - (make-bitcoin-cross-toolchain target #:base-libc glibc-2.27/bitcoin-patched))
  + (make-bitcoin-cross-toolchain target
  + #:base-libc glibc-2.27/bitcoin-patched
  + #:base-kernel-headers linux-libre-headers-4.19))
  (else
  (make-bitcoin-cross-toolchain target)))))
  ((string-contains target "darwin")
  