configure: fix log corruption with option -v

This bug occurs if ./configure is called with -v on systems on
which fd proc entries point to the files/devices they are open
on instead of being magic nodes which would basically dup() the
actual fds (e.g., Linux).

In this case, the command "tee $tty" appends to /dev/stderr, which
may be already opened by the parent process. This breaks the log file.

Normally, the log file starts with

 This is the Qt Open Source Edition.
 ...

but with `-v` flag it would start with output of awkprog and maybe
some zero bytes. Zero bytes are observed on Debian Wheezy.

 DEFAULT_INCDIRS=...
 ...
 ^@^@^@^@^@^@^@^@^@^@^@^@...
 Done running configuration tests.
 ...

To fix this problem, the output of `...` is saved to a variable, and
then eval'd and echo'd (if -v).

This solution was found by Tony Theodore.
https://github.com/mxe/mxe/issues/938#issuecomment-149770348

Change-Id: Id0c28598890e813774cc92f38ee46a0697b34e77
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/configure b/configure
index 3fbf97143d..367cb22455 100755
--- a/configure
+++ b/configure
@@ -3613,10 +3613,9 @@ END {
         print "DEFAULT_LIBDIRS=\"/lib\n/usr/lib\"\n";
 }'
 
-unset tty
-[ "$OPT_VERBOSE" = "yes" ] && tty=/dev/stderr
-eval "`LC_ALL=C $TEST_COMPILER $SYSROOT_FLAG $TEST_COMPILER_CXXFLAGS -xc++ -E -v - < /dev/null 2>&1 > /dev/null | $AWK "$awkprog" | tee $tty`"
-unset tty
+awkprog_result=`LC_ALL=C $TEST_COMPILER $SYSROOT_FLAG $TEST_COMPILER_CXXFLAGS -xc++ -E -v - < /dev/null 2>&1 > /dev/null | $AWK "$awkprog"`
+eval "$awkprog_result"
+[ "$OPT_VERBOSE" = "yes" ] && echo "$awkprog_result"
 
 echo "Done running configuration tests."