configure: Enable -C rpath by default

This commit changes our distribution and in-tree sources to pass the `-C rpath`
flag by default during compiles. This means that from-source builds, including
our release channels, will have this option enabled as well. Motivated
by #29941, this change means that the compiler should be usable as-is on all
platforms just after extraction or installation. This experience is already true
on Windows but on Unixes you still need to set up LD_LIBRARY_PATH or the
equivalent, which can often be unfortunate.

This option was originally turned off by default for Linux distributions who
tend to take care of these sorts of details themselves, so it is expected that
all those builds of Rust will want to pass `--disable-rpath` to the configure
script to preserve that behavior.

Closes #29941

configure

@@ -587,7 +587,7 @@ opt fast-make 0 "use .gitmodules as timestamp for submodule deps"
 opt ccache 0 "invoke gcc/clang via ccache to reuse object files between builds"
 opt local-rust 0 "use an installed rustc rather than downloading a snapshot"
 opt llvm-static-stdcpp 0 "statically link to libstdc++ for LLVM"
-opt rpath 0 "build rpaths into rustc itself"
+opt rpath 1 "build rpaths into rustc itself"
 opt stage0-landing-pads 1 "enable landing pads during bootstrap with stage0"
 # This is used by the automation to produce single-target nightlies
 opt dist-host-only 0 "only install bins for the host architecture"