build: avoid false -Wmaybe-uninitialized warnings

Allow easily building a debug build for example with:
  make CFLAGS='-O0 -ggdb'

False -Wmaybe-uninitialized warnings hit in different
places depending on the compiler passes used.
These changes were tested with gcc 10.2.1, 12.2.1, and 13.1.1 like:
  for o in g s z fast 0 1 2 3; do
    make clean && make -j$(nproc) CFLAGS="-O$o" || break
  done

* src/digest.c: Disable -Wmaybe-uninitialized that gives
false positive here at -O0.
* src/ln.c: Avoid -Wmaybe-uninitialized that gives
false positive here at -O1.
* src/pr.c: Likewise.
* src/sort.c: Likewise.
* src/tee.c: Avoid -Wmaybe-uninitialized that gives
false positive here at -O3 on gcc 13.1.1 at least.
* src/cp.c: Avoid -Wmaybe-uninitialized that gives
false positive here at -Os on gcc 13.1.1 at least.
* src/copy.c: Avoid -Wmaybe-uninitialized that gives
false positive here at -Og on gcc 13.1.1 at least.
* src/head.c: Likewise.
* src/paste.c: Likewise.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/paste.c b/src/paste.c
index 5c194d8fe..468ef3ab0 100644
--- a/src/paste.c
+++ b/src/paste.c
@@ -233,7 +233,7 @@ paste_parallel (size_t nfiles, char **fnamptr)
 
       for (size_t i = 0; i < nfiles && files_open; i++)
         {
-          int chr;			/* Input character. */
+          int chr IF_LINT ( = -1);	/* Input character. */
           int err;			/* Input errno value.  */
           bool sometodo = false;	/* Input chars to process.  */