auto merge of #14832 : alexcrichton/rust/no-rpath, r=brson

This commit disables rustc's emission of rpath attributes into dynamic libraries
and executables by default. The functionality is still preserved, but it must
now be manually enabled via a `-C rpath` flag.

This involved a few changes to the local build system:

* --disable-rpath is now the default configure option
* Makefiles now prefer our own LD_LIBRARY_PATH over the user's LD_LIBRARY_PATH
  in order to support building rust with rust already installed.
* The compiletest program was taught to correctly pass through the aux dir as a
  component of LD_LIBRARY_PATH in more situations.

The major impact of this change is that neither rustdoc nor rustc will work
out-of-the-box in all situations because they are dynamically linked. It must be
arranged to ensure that the libraries of a rust installation are part of the
LD_LIBRARY_PATH. The default installation paths for all platforms ensure this,
but if an installation is in a nonstandard location, then configuration may be
necessary.

Additionally, for all developers of rustc, it will no longer be possible to run
$target/stageN/bin/rustc out-of-the-box. The old behavior can be regained
through the `--enable-rpath` option to the configure script.

This change brings linux/mac installations in line with windows installations
where rpath is not possible.

Closes #11747
[breaking-change]

configure

@@ -418,7 +418,7 @@ 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 inject-std-version 1 "inject the current compiler version of libstd into programs"
 opt llvm-static-stdcpp 0 "statically link to libstdc++ for LLVM"
-opt rpath 1 "build rpaths into rustc itself"
+opt rpath 0 "build rpaths into rustc itself"
 opt nightly 0 "build nightly packages"
 opt verify-install 1 "verify installed binaries work"
 opt jemalloc 1 "build liballoc with jemalloc"

man/rustc.1

@@ -138,8 +138,8 @@ A space-separated list of arguments to pass through to LLVM.
 If specified, the compiler will save more files (.bc, .o, .no-opt.bc) generated
 throughout compilation in the output directory.
 .TP
-\fBno-rpath\fR
-If specified, then the rpath value for dynamic libraries will not be set in
+\fBrpath\fR
+If specified, then the rpath value for dynamic libraries will be set in
 either dynamic library or executable outputs.
 .TP
 \fBno-prepopulate-passes\fR

mk/main.mk

@@ -122,8 +122,8 @@ endif
 ifdef TRACE
   CFG_RUSTC_FLAGS += -Z trace
 endif
-ifdef CFG_DISABLE_RPATH
-CFG_RUSTC_FLAGS += -C no-rpath
+ifdef CFG_ENABLE_RPATH
+CFG_RUSTC_FLAGS += -C rpath
 endif
 
 # The executables crated during this compilation process have no need to include

src/librustc/back/link.rs

@@ -1363,7 +1363,7 @@ fn link_args(cmd: &mut Command,
         if sess.targ_cfg.os == abi::OsMacos {
             cmd.args(["-dynamiclib", "-Wl,-dylib"]);
 
-            if !sess.opts.cg.no_rpath {
+            if sess.opts.cg.rpath {
                 let mut v = Vec::from_slice("-Wl,-install_name,@rpath/".as_bytes());
                 v.push_all(out_filename.filename().unwrap());
                 cmd.arg(v.as_slice());
@@ -1382,7 +1382,7 @@ fn link_args(cmd: &mut Command,
     // FIXME (#2397): At some point we want to rpath our guesses as to
     // where extern libraries might live, based on the
     // addl_lib_search_paths
-    if !sess.opts.cg.no_rpath {
+    if sess.opts.cg.rpath {
         cmd.args(rpath::get_rpath_flags(sess, out_filename).as_slice());
     }
 

src/librustc/driver/config.rs

@@ -306,8 +306,8 @@ cgoptions!(
         "a list of arguments to pass to llvm (space separated)"),
     save_temps: bool = (false, parse_bool,
         "save all temporary output files during compilation"),
-    no_rpath: bool = (false, parse_bool,
-        "disables setting the rpath in libs/exes"),
+    rpath: bool = (false, parse_bool,
+        "set rpath values in libs/exes"),
     no_prepopulate_passes: bool = (false, parse_bool,
         "don't pre-populate the pass manager with a list of passes"),
     no_vectorize_loops: bool = (false, parse_bool,