AC_COMPILE_ELSEIF and AC_LINK_ELSEIF misdetections

[Jeffrey Walton]

Hi Everyone,

In case this can make it into the upcoming release...

AC_COMPILE_ELSEIF and AC_LINK_ELSEIF often misdetects which results in
bad configurations and broken compiles on AIX with XL C/C++ and
Solaris with SunCC. We found we can't use the macros.

We use the following string to detect bad results from running the
compiler, linker and assembler:

    BAD_RESULT="fatal|error|unknown|unrecognized|illegal|not found|not
exist|cannot find"

For example, "illegal" is present because the SunCC compiler emits
"illegal option" for, say, -xarch=sha. At the moment Sun Studio 12.6
and SunCC does not provide the GCC equivalent to -msha. However an
AC_COMPILE_ELSEIF reports success when the illegal option is present.

Jeff