ghc should appear as inplace/bin/ghc-stage2.exe after a successful build.
The warnings are expected.
Did you run make with parallelism? I don't have a smoking gun, but the build seems to be somewhat stable with -j1, while it crashes a lot of the time with -j5 (I have a 4-core CPU). I have only tried a couple of runs with -j1 (takes a while...), so I can't say for sure that non-parallel builds are stable, but 2/2 runs succeeded.
Another data point: I ran the validate script in a loop and stored the logs, and most crashes seem to be in rts/, but not all of them. Not sure why.
$ grep Segmentation *.log
1.log:make[1]: *** [libraries/base/dist-install/build/Text/Show/Functions.o] Segmentation fault
10.log:make[1]: *** [rts/dist/build/Hpc.o] Segmentation fault
11.log:make[1]: *** [rts/dist/build/RtsFlags.thr_l_o] Segmentation fault
12.log:make[1]: *** [rts/dist/build/sm/GCAux.o] Segmentation fault
13.log:make[1]: *** [rts/dist/build/win32/GetEnv.thr_l_o] Segmentation fault
14.log:make[1]: *** [rts/dist/build/sm/Scav.l_o] Segmentation fault
15.log:make[1]: *** [compiler/stage1/build/RegAlloc/Linear/State.o] Segmentation fault
18.log:make[1]: *** [libraries/filepath/dist-install/build/.depend-v.haskell] Segmentation fault
19.log:make[1]: *** [libraries/base/dist-install/build/.depend-v.haskell] Segmentation fault
4.log:make[1]: *** [rts/dist/build/RtsDllMain.o] Segmentation fault
5.log:make[1]: *** [rts/dist/build/sm/Evac_thr.thr_o] Segmentation fault
6.log:make[1]: *** [rts/dist/build/sm/Scav_thr.thr_l_o] Segmentation fault
7.log:make[1]: *** [rts/dist/build/Linker.thr_debug_o] Segmentation fault
8.log:make[1]: *** [rts/dist/build/sm/Storage.debug_o] Segmentation fault
9.log:make[1]: *** [rts/dist/build/hooks/OutOfHeap.thr_debug_o] Segmentation fault