[LLVMdev] Add --program-prefix support with AC_CANONICAL_TARGET override.

[Rick Foos]

Adding --program-prefix support to the autoconf build has been an adventure.

A patch was applied. It worked on the usual llvm bots, but failed on 
other bots with different configure options.

The patch was reverted as it broke on bots specifying --build, --host, 
and --target in configure.

An option is proposed here to change the behavior of program-prefix to 
it's normal behavior when AC_CANONICAL_TARGET is not specified. Meaning 
--program-prefix can only be set from the configure command line.

--- background

LLVM autoconf/configure.ac uses the AC_CANONICAL_TARGET.

This rule adds a test that can set program_prefix=target if 
--program-prefix is not specified on the configure line.
test -n "$target_alias" &&
   test "$program_prefix$program_suffix$program_transform_name" = \
     NONENONEs,x,x, &&
   program_prefix=${target_alias}-[]dnl

./configure --target=blah
results in
program_prefix=blah

--- Proposed patch

The original patch has been updated to ignore the test added by 
AC_CANONICAL_TARGET. Program prefix can only be set from the command 
line of configure.

./configure --target=blah
results in
program_prefix=

./configure --target=blah --program-prefix=blah
results in
program_prefix=blah

The attached patches reflect the code to do this change.

-rick

-- 
Rick Foos
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

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