Add a space to work around a Windows CPython / MSys quoting bug

[rnk]

Summary

The rules for quoting the command line that a subprocess receives are
user space conventions implemented by the C runtime. Python's quoting
rules are implemented here:
https://github.com/python/cpython/blob/c30098c8c6014f3340a369a31df9c74bdbacc269/Lib/subprocess.py#L725

The result is that the final command line C string computed by Python is
'echo \"'. Mingw doesn't appear to interpret that backslash as escaping
the quote because it is not already inside a quoted region. As a result,
our echo command prints a single backslash instead of a quote.

The whole issue can be sidestepped by adding a space a forcing Python to
put the argument to echo in double quotes.

[inglorion]

lgtm, thanks!

[ruiu]

LGTM

lld/trunk/test/ELF/libsearch.s

 // RUN: ld.lld -o %t3 %t.o -L%t.dir -static -lls
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=STATIC %s
 // RUN: ld.lld -o %t3 %t.o -L%t.dir -Bstatic -dy -lls
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=DYNAMIC %s
 // RUN: ld.lld -o %t3 %t.o -L%t.dir -Bstatic -call_shared -lls
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=DYNAMIC %s
 
 // -nostdlib
-// RUN: echo 'SEARCH_DIR("'%t.dir'")' > %t.script
+// RUN: echo ' SEARCH_DIR("'%t.dir'")' > %t.script
 // RUN: ld.lld -o %t3 %t.o -script %t.script -lls
 // RUN: not ld.lld -o %t3 %t.o -script %t.script -lls -nostdlib \
 // RUN:   2>&1 | FileCheck --check-prefix=NOSTDLIB %s
 // NOSTDLIB: unable to find library -lls
 
 .globl _start,_bar
 _start:

lld/trunk/test/ELF/version-script-err.s

 // REQUIRES: x86
 
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 // RUN: not ld.lld -shared %t.o -o %t.so --version-script %p/Inputs/version-script-err.script 2>&1 | FileCheck %s
 // CHECK: ; expected, but got }
 
-// RUN: echo    "\"" > %terr1.script
+// RUN: echo    " \"" > %terr1.script
 // RUN: not ld.lld --version-script %terr1.script -shared %t.o -o %t.so 2>&1 | \
 // RUN:   FileCheck -check-prefix=ERR1 %s
 // ERR1: unclosed quote