We were using the Typeable.hs macros, but for no good reason as
far as I can tell.

I also made the -ffloat-all-lams flag not take an argument, as it just
ignored it.

Makes it consistent with the existing "C compiler flags"
field.

Rather than using the compiler that configure detects, we use
the "GCC command" field from the --info output of the bootstrapping
compiler (provided it is >= 7.1).

This allows different gcc's to be used when building different stages,
which we need to do when cross-compiling.

It couldn't be overridden, and was defined as YES.

We always are, nowadays.

This reverts commit b1f453e1.
It caused dynHelloWorld(dyn) to fail.

They were hardcoded in Config.hs

This allows tools like Linux's perf events to display symbol names for
CMM primops.

The pgm* fields are already in Settings

We were doing
    echo $(HOSTPLATFORM) | sed 's/i[567]86/i486/g'
but the only x86 value HOSTPLATFORM can have is i386.

We now tell libffi its build platform again, but we now tell it it's
$(BUILDPLATFORM) rather than $(HOSTPLATFORM).

The value --build was set to broke cross-compilier builds, and isn't
needed for regular builds.

Stops us having to temporarily have a panic in the DynFlags.
We still need a panic in the DynFlags used for the top-level
error handler, though.

Based on an idea from Karel Gardas, who had troubles with the original
sed version (which didn't work with /usr/bin/sed on Solaris).

of 'invalid ELF header'.

versions of Fedora. The INPUT command is use by libncursesw.so in
Fedora.

This just a refactoring, removing dead code

Some out of date code in TcErrors was suppressing an error
report -- so some type-incorrect code leaked out and confused
a later bit of the compiler.