v8: build with gcc6

[xeji]

Motivation for this change

Doesn't build with gcc7 due to this issue in upstream code.

/cc ZHF #36453 - please backport to 18.03

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

[ryantm]

@GrahamcOfBorg eval

[Mic92]

@GrahamcOfBorg build v8

[GrahamcOfBorg]

Failure on x86_64-darwin (full log)

Partial log (click to expand)

  ACTION Generating icuuc shim headers _private_tmp_nix_build_v8_5_4_232_drv_0_source_third_party_icu_icu_gyp_icuuc_target_generate_icuuc_shim_headers.intermediate
  TOUCH /private/tmp/nix-build-v8-5.4.232.drv-0/source/out/Release/obj.target/third_party/icu/icuuc.stamp
  CXX(target) /private/tmp/nix-build-v8-5.4.232.drv-0/source/out/Release/obj.target/v8_libbase/src/base/accounting-allocator.o
g++: error: unrecognized command line option '-Wshorten-64-to-32'
g++: error: unrecognized command line option '-stdlib=libc++'
make: *** [src/v8_libbase.target.mk:198: /private/tmp/nix-build-v8-5.4.232.drv-0/source/out/Release/obj.target/v8_libbase/src/base/accounting-allocator.o] Error 1
rm _private_tmp_nix_build_v8_5_4_232_drv_0_source_third_party_icu_icu_gyp_icuuc_target_generate_icuuc_shim_headers.intermediate _private_tmp_nix_build_v8_5_4_232_drv_0_source_third_party_icu_icu_gyp_icui18n_target_generate_icui18n_shim_headers.intermediate
make: Leaving directory '/private/tmp/nix-build-v8-5.4.232.drv-0/source/out'
builder for '/nix/store/ac518bv50r1jxyhil70pk5z8argk1ci4-v8-5.4.232.drv' failed with exit code 2
error: build of '/nix/store/ac518bv50r1jxyhil70pk5z8argk1ci4-v8-5.4.232.drv' failed

[GrahamcOfBorg]

Success on aarch64-linux (full log)

Partial log (click to expand)

shrinking /nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232/bin/d8
strip is /nix/store/lvx1acn1ig1j2km8jds5x3ggh3f2wa8v-binutils-2.28.1/bin/strip
stripping (with command strip and flags -S) in /nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232/lib  /nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232/bin
patching script interpreter paths in /nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232
checking for references to /build in /nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232...
shrinking RPATHs of ELF executables and libraries in /nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232
shrinking /nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232/lib/libv8.so
shrinking /nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232/bin/d8
shrinking /nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232/bin/mksnapshot
/nix/store/zr817iiq153fc1r9whai7l0ng571vkr2-v8-5.4.232

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Partial log (click to expand)

shrinking /nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232/lib/libv8.so
strip is /nix/store/b0zlxla7dmy1iwc3g459rjznx59797xy-binutils-2.28.1/bin/strip
stripping (with command strip and flags -S) in /nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232/lib  /nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232/bin
patching script interpreter paths in /nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232
checking for references to /build in /nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232...
shrinking RPATHs of ELF executables and libraries in /nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232
shrinking /nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232/bin/d8
shrinking /nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232/bin/mksnapshot
shrinking /nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232/lib/libv8.so
/nix/store/2rrq4c2c5wfnl0qgifdnkzy6lm7v30xf-v8-5.4.232

[xeji]

The build on darwin was broken since Feb 16 (https://hydra.nixos.org/build/69365537).
With this change it still fails but for what looks like a different reason.
So should we merge this anyway and fix darwin later?

[Mic92]

Can you alter the compiler only on linux and not on darwin at least?

[xeji]

sure, will do

[xeji]

limited the compiler change to linux and squashed into one commit

[Mic92]

backport in 3c4c591

[xeji]

cc #31747