intel compiler: fix link time error with LLVMgold.so (#28731)

The Intel compiler will, at link time, call `ld -plugin LLVMgold.so`, which
expects libraries like `libimfo.so` to be found either in the `LD_LIBRARY_PATH` or
in `LLVMgold.so`s RPATH.

As `LLVMgold.so` already uses RUNPATH, I used that to extend this to the
necessary library locations.

This PR should fix issues:
https://github.com/spack/spack/issues/10308
https://github.com/spack/spack/issues/18606
https://github.com/spack/spack/issues/17100
https://github.com/spack/spack/issues/21237
https://github.com/spack/spack/issues/4261

Co-authored-by: Stephen Sachs <stesachs@amazon.com>

lib/spack/spack/build_systems/intel.py

@@ -24,6 +24,7 @@
     install,
 )
 
+import spack.error
 from spack.build_environment import dso_suffix
 from spack.package import InstallError, PackageBase, run_after
 from spack.util.environment import EnvironmentModifications
@@ -1333,5 +1334,42 @@ def uninstall_ism(self):
         debug_print(os.getcwd())
         return
 
+    @property
+    def base_lib_dir(self):
+        """Provide the library directory located in the base of Intel installation.
+        """
+        d = self.normalize_path('')
+        d = os.path.join(d, 'lib')
+
+        debug_print(d)
+        return d
+
+    @run_after('install')
+    def modify_LLVMgold_rpath(self):
+        """Add libimf.so and other required libraries to the RUNPATH of LLVMgold.so.
+
+        These are needed explicitly at dependent link time when
+        `ld -plugin LLVMgold.so` is called by the compiler.
+        """
+        if self._has_compilers:
+            LLVMgold_libs = find_libraries('LLVMgold', self.base_lib_dir,
+                                           shared=True, recursive=True)
+            # Ignore ia32 entries as they mostly ignore throughout the rest
+            # of the file.
+            # The first entry in rpath preserves the original, the seconds entry
+            # is the location of libimf.so. If this relative location is changed
+            # in compiler releases, then we need to search for libimf.so instead
+            # of this static path.
+            for lib in LLVMgold_libs:
+                if not self.spec.satisfies('^patchelf'):
+                    raise spack.error.SpackError(
+                        'Attempting to patch RPATH in LLVMgold.so.'
+                        + '`patchelf` dependency should be set in package.py'
+                    )
+                patchelf = Executable('patchelf')
+                rpath = ':'.join([patchelf('--print-rpath', lib, output=str).strip(),
+                                  '$ORIGIN/../compiler/lib/intel64_lin'])
+                patchelf('--set-rpath', rpath, lib)
+
     # Check that self.prefix is there after installation
     run_after('install')(PackageBase.sanity_check_prefix)