gnu: linux-libre: Remove '--strip-all' argument.

* gnu/packages/linux.scm (linux-libre)[arguments]: Remove
  #:strip-flags, which led to unloadable modules.  This reverts
  commit 9ca7eaa1.
  [build-phase]: Add INSTALL_MOD_STRIP=1.

gnu/packages/linux.scm

@@ -249,6 +249,7 @@ (define-public linux-libre
                                (string-append "MODULE_DIR=" moddir)
                                (string-append "INSTALL_PATH=" out)
                                (string-append "INSTALL_MOD_PATH=" out)
+                               "INSTALL_MOD_STRIP=1"
                                "modules_install"))))))
    (package
     (name "linux-libre")
@@ -275,7 +276,6 @@ (define-public linux-libre
                   (guix build utils)
                   (srfi srfi-1)
                   (ice-9 match))
-       #:strip-flags '("--strip-all")
        #:phases (alist-replace
                  'build ,build-phase
                  (alist-replace