eric wrotelast version of icecat available on testing repo.
Installed, Works like a charm. Thanks again eric :)

Edit: Please repackage without dbus-glib dependency! [0]

[0] https://github.com/Obarun/obarun-pkgbuild-testing/blob/master/icecat/PKGBUILD# L20 404'd (Archived here:https://archive.is/aRzcM# 20%)

For instance this is from *my* pkgbuild and pkg.tar.xz 
taco@ zen gcc5 % cat ../PKGBUILD| grep depends
depends=('gtk2' 'mozilla-common' 'libxt' 'startup-notification' 'mime-types'
makedepends=('unzip' 'zip' 'diffutils' 'python2' 'yasm' 'mesa' 'imake'
optdepends=('networkmanager: Location detection via available WiFi networks'
taco@ zen gcc5 % pacman -Qi --file icecat-38.8.0-3-x86_64.pkg.tar.xz | grep Depends 
Depends On      : gtk2  mozilla-common  libxt  startup-notification  mime-types  alsa-lib  desktop-file-utils  hicolor-icon-theme  libvpx  icu  libevent  nss  hunspell  sqlite  pango  freetype2  libxft  libx11
Notice how dbus-glib isn't in mine :)

P.S Stop scaring me, eric. lol
oh yes, good catch, forgotten this :)
16 days later
Just a note, CRUX linux has updated gcc to 5.4 which (possibly) means that will work on edge cases like this
12 days later
Update: 6/20/16
IceCat needs to rebuilt with gcc 5 and the latest hunspell (at the time of this post: 1.4.1-1)
taco@ zen ~ % icecat
XPCOMGlueLoad error for file /usr/lib/icecat/libxul.so:
libhunspell-1.3.so.0: cannot open shared object file: No such file or directory
Couldn't load XPCOM.
taco@ zen [255] ~ %
8 days later
Update: Wed Jun 29 00:50:08 UTC 2016
Good news,It looks like parabola devs have patched around the gcc6 issue 6~ days ago (at the time of this post) [0]
Based on two bug reports from archlinux :)
GNU/Icecat commit wrote* GCC6 is not officially supported and lot of patches have been added.
I strongly suggest to backport the patches. [1] [2] and possibly the harfbuzz [3] [4] and install dir [5] patches.

I will test this in a few days (without dbus, pulseaudio and the disable-crypto-hardening-settings.patch of course ^^).

[0] gcc6-fix-compilation-for-IceCat.patch message
[1] gcc6-fix-compilation-for-IceCat.patch
[2] firefox-gcc-6.0.patch
[3] harfbuzz-1.1.3.patch
[4] mozilla-1228540-1.patch
[5] icecat-install-dir.patch

Update: Fri Jul 1 02:11:52 UTC 2016
Icecat successfully builds with GCC 6 from the patches provided by parabola! 
==> Tidying install...
  -> Removing empty directories...
  -> Removing libtool files...
  -> Purging unwanted files...
  -> Removing static library files...
  -> Stripping unneeded symbols from binaries and libraries...
  -> Compressing man and info pages...
==> Checking for packaging issue...
==> Creating package "icecat"...
  -> Generating .PKGINFO file...
  -> Generating .BUILDINFO file...
  -> Adding install file...
  -> Generating .MTREE file...
  -> Compressing package...
==> Creating package "icecat-debug"...
  -> Generating .PKGINFO file...
  -> Generating .BUILDINFO file...
  -> Generating .MTREE file...
  -> Compressing package...
==> Leaving fakeroot environment.
==> Finished making: icecat 38.8.0_gnu2-1 (Thu Jun 30 21:00:43 CDT 2016)
==> Cleaning up...
==> Removing installed dependencies...
checking dependencies...

Packages (2) imake-1.0.7-1  yasm-1.3.0-1

Total Removed Size:  4.92 MiB

:: Do you want to remove these packages? [Y/n] Y
:: Processing package changes...
(1/2) removing yasm                                                 [# #####################################] 100%
(2/2) removing imake                                                [# #####################################] 100%
:: Running post-transaction hooks...
(1/1) Purging old manpage index entries...
taco@ zen IceCat-Parabola % gcc --version
gcc (GCC) 6.1.1 20160602
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
There's a few changes I made to the PKGBUILD here, you can compare it with the one provided by parabola.
8 days later
ok, thanks for the report, i will compile it again when i have time, probably this week-end. Thanks to follow this package carefully :)
a month later
icecat needs to be rebuilt with libvpx 1.6.0 otherwise it will fail to start. Please make that change.


Also icecat.install is now redundant since it compiles with gcc6 [0] 
post_install() {
  cat <<MSG
>>> This package fail to build with gcc6.
	It was build with this toolchain :
	binutils-2.26-3  gcc-5.3.0-5  gcc-libs-5.3.0-5 
	glibc-2.23-1 llvm-3.7.1-1 llvm-libs-3.7.1-1 clang-3.7.1-1
MSG
}
[0] https://github.com/Obarun/obarun-pkgbuild/blob/master/icecat/icecat.install
done, thanks :)

note: grr i forgot to erase the post install message, it will be made on the next release
21 days later
bit wrote CRUX
Isn't crux DEAD ? ? ?
a year later
An error again (similar to one mentioned in post # 25 above): 
vn@ lx ~ % icecat
XPCOMGlueLoad error for file /usr/lib/icecat/libxul.so:
libicui18n.so.59: cannot open shared object file: No such file or directory
Couldn't load XPCOM.
vn@ lx [255] ~ %
archie wrote
bit wrote CRUX
Isn't crux DEAD ? ? ?
Where did you get this information?
crux is very much alive used it a few months back, its a net install just like arch no installer uses the same bsd init scripts that inspired arch and a ports system
@ ray, sorry but this package should be maintained by bit. Apparently, he doesn't come here anymore and i do not have time to maintain this package. I need to remove it from the repo.
@ eric, ok no problem. I've just tried to compile it from aur recently, but without success. Then I came accross this thread and tried the binary from your repo. So I decided to show the bug.
ray wrote@ eric, ok no problem. I've just tried to compile it from aur recently, but without success. Then I came accross this thread and tried the binary from your repo. So I decided to show the bug.
To build the AUR package you need to manually import the key its in the comments. or you can use icecat-bin also in AUR, but you are better off using palemoon or waterfox.
eric, mandog, thanks for comments, well noted. And parabola package runs well.

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