In both a poudriere jail and normal 9.3r45 host FreeBSD 9.3p45 fails to build devel/llvm36 with the following error:

.....
llvm[1]: Building Intrinsics.gen.tmp from Intrinsics.td
llvm-tblgen: Unknown command line argument '-I'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/lib/IR'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '-I'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/include'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '-I'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/include'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '-I'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/lib/Target'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/include/llvm/IR/Intrinsics.td'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '-o'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/lib/IR/Release/Intrinsics.gen.tmp'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
llvm-tblgen: Unknown command line argument '-gen-intrinsic'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
gmake[1]: *** [Makefile:24: /usr/ports/devel/llvm36/work/llvm-3.6.2.src/lib/IR/Release/Intrinsics.gen.tmp] Error 1
gmake[1]: Leaving directory '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/lib/IR'
gmake: *** [/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Makefile.rules:883: all] Error 1
*** [do-build] Error code 1

Stop in /usr/ports/devel/llvm36.
*** [stage] Error code 1

Something seems odd with the llvm-tblgen program:

$ /usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help
llvm-tblgen: Unknown command line argument '-help'.  Try: '/usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen -help'
$ /usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen
Stack dump:
0.      Program arguments: /usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen 
Segmentation fault: 11

$ gdb /usr/ports/devel/llvm36/work/llvm-3.6.2.src/Release/bin/llvm-tblgen ./llvm-tblgen.core 
GNU gdb 6.1.1 [FreeBSD]
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "amd64-marcel-freebsd"...(no debugging symbols found)...
Core was generated by `llvm-tblgen'.
Program terminated with signal 11, Segmentation fault.
Reading symbols from /lib/libz.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/libz.so.6
Reading symbols from /lib/libthr.so.3...(no debugging symbols found)...done.
Loaded symbols for /lib/libthr.so.3
Reading symbols from /usr/local/lib/libedit.so.0...(no debugging symbols found)...done.
Loaded symbols for /usr/local/lib/libedit.so.0
Reading symbols from /lib/libncurses.so.8...(no debugging symbols found)...done.
Loaded symbols for /lib/libncurses.so.8
Reading symbols from /usr/local/lib/gcc48/libstdc++.so.6...Error while reading shared library symbols:
Dwarf Error: wrong version in compilation unit header (is 4, should be 2) [in module /usr/local/lib/gcc48/libstdc++.so.6]
Reading symbols from /lib/libm.so.5...(no debugging symbols found)...done.
Loaded symbols for /lib/libm.so.5
Reading symbols from /usr/local/lib/gcc48/libgcc_s.so.1...Error while reading shared library symbols:
Dwarf Error: wrong version in compilation unit header (is 4, should be 2) [in module /usr/local/lib/gcc48/libgcc_s.so.1]
Reading symbols from /lib/libc.so.7...(no debugging symbols found)...done.
Loaded symbols for /lib/libc.so.7
Reading symbols from /libexec/ld-elf.so.1...(no debugging symbols found)...done.
Loaded symbols for /libexec/ld-elf.so.1
#0  0x0000000000540be1 in llvm::Twine::toStringRef ()
[New Thread 802007400 (LWP 100194/llvm-tblgen)]
(gdb) bt
#0  0x0000000000540be1 in llvm::Twine::toStringRef ()
#1  0x00000000005372df in llvm::MemoryBuffer::getFileOrSTDIN ()
#2  0x00000000005066c3 in llvm::TableGenMain ()
#3  0x0000000000406c24 in main ()
(gdb) 

Building with and without MAKE_JOBS_UNSAFE=yes has no difference.
I was able to build devel/lang36 on 08/11/16.