libintl, iconv, gettext: account for libc provider and externals (#35450)

* libiconv can be provided by libc, so update packages which depend on
  libiconv to require the iconv virtual instead
* Many packages need special consideration when locating iconv depending
  on whether it is provided by libc (no prefix provided) or the libiconv
  package (in that case we want to provide a prefix)
* It was also noticed that when an iconv external was provided, that
  there was interference with linking (this should generally be handled
  by Spack's compiler wrappers and bears further investigation)
* Like iconv, libintl can be provided by libc or another package, namely
  gettext. It is not converted to a provider like libiconv because it
  provides additional routines. The logic is similar to that of iconv
  but instead of checking the provider, we check whether the gettext
  installation includes libintl.

1 files changed, 5 insertions, 5 deletions

diff --git a/var/spack/repos/builtin/packages/bcache/package.py b/var/spack/repos/builtin/packages/bcache/package.py
index 4f24bd9cd7..724e4dff19 100644
--- a/var/spack/repos/builtin/packages/bcache/package.py
+++ b/var/spack/repos/builtin/packages/bcache/package.py
@@ -24,16 +24,16 @@ class Bcache(MakefilePackage):
     depends_on("gettext")
     depends_on("pkgconfig", type="build")
 
-    def setup_build_environment(self, env):
-        # Add -lintl if provided by gettext, otherwise libintl is provided by the system's glibc:
-        if "gettext" in self.spec and "intl" in self.spec["gettext"].libs.names:
-            env.append_flags("LDFLAGS", "-lintl")
-
     patch(
         "func_crc64.patch",
         sha256="558b35cadab4f410ce8f87f0766424a429ca0611aa2fd247326ad10da115737d",
     )
 
+    def flag_handler(self, name, flags):
+        if name == "ldflags" and "intl" in self.spec["gettext"].libs.names:
+            flags.append("-lintl")
+        return self.env_flags(name, flags)
+
     def install(self, spec, prefix):
         mkdirp(prefix.bin)
         install("bcache-register", prefix.bin)