Windows broken

[Simon Peyton Jones]

Help please!
Suddenly my Windows build has stopped working.   See below.  What should I do?  I'm totally stuck.
This has never happened before.
I get this:

GHC path canonicalised to: c:/fp/ghc-8.0.2/bin/ghc

checking build system type... x86_64-pc-msys

checking host system type... x86_64-pc-msys

checking target system type... x86_64-pc-msys

Build platform inferred as: x86_64-unknown-mingw32

Host platform inferred as: x86_64-unknown-mingw32

Target platform inferred as: x86_64-unknown-mingw32

GHC build  : x86_64-unknown-mingw32

GHC host   : x86_64-unknown-mingw32

GHC target : x86_64-unknown-mingw32

LLVM target: x86_64-unknown-mingw32

checking for path to top of build tree... C:/code/HEAD

configure: Checking for Windows toolchain tarballs...

configure: Extracting Windows toolchain from archives (may take a while)...

configure: In-tree MingW-w64 tree created

configure: Making in-tree perl tree

configure: In-tree perl tree created

checking whether the C compiler works... no

configure: error: in `/c/code/HEAD':

configure: error: C compiler cannot create executables

See `config.log' for more details
Something wrong with the gcc.exe?  Config.log has this

gcc version 6.3.0 (Rev2, Built by MSYS2 project)

configure:4950: $? = 0

configure:4939: C:/code/HEAD/inplace/mingw/bin/gcc.exe -V >&5

gcc.exe: error: unrecognized command line option '-V'

gcc.exe: fatal error: no input files

compilation terminated.

configure:4950: $? = 1

configure:4939: C:/code/HEAD/inplace/mingw/bin/gcc.exe -qversion >&5

gcc.exe: error: unrecognized command line option '-qversion'; did you mean '--version'?

gcc.exe: fatal error: no input files

compilation terminated.

configure:4950: $? = 1

configure:4970: checking whether the C compiler works

configure:4992: C:/code/HEAD/inplace/mingw/bin/gcc.exe    conftest.c  >&5

configure:4996: $? = 1

configure:5034: result: no

configure: failed program was:

| /* confdefs.h */

| #define PACKAGE_NAME "The Glorious Glasgow Haskell Compilation System"

| #define PACKAGE_TARNAME "ghc-8.3"

| #define PACKAGE_VERSION "8.3"

| #define PACKAGE_STRING "The Glorious Glasgow Haskell Compilation System 8.3"

| #define PACKAGE_BUGREPORT "glasgow-haskell-bugs at haskell.org"

| #define PACKAGE_URL ""

| /* end confdefs.h.  */

|

| int

| main ()

| {

|

|   ;

|   return 0;

| }

configure:5039: error: in `/c/code/HEAD':

configure:5041: error: C compiler cannot create executables
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