patch 9.0.2028: confusing build dependencies

Problem:  confusing build dependencies
Solution: clean them up, make them parallelizable

Separate vim binary and unittest dependencies, make them parallelizable

Clean up make dependencies so Vim and unit test binaries only depend on
the object files they need. This fixes an existing issue where after
running unit tests, the Vim binary would be invalidated, which results
in it having to be linked again when running script tests, even though
Vim was already previously built.

Make link.sh (script we use to link those binaries) generate namespaced
temporary files for each app to avoid them colliding with each other.
This allows `unittesttargets` to be built in parallel.

These fixes are useful when using link-time-optimization as the link
phase could now take minutes rather than a few seconds.

closes: #13344

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>
diff --git a/src/link.sh b/src/link.sh
index 71ee061..e4030de 100755
--- a/src/link.sh
+++ b/src/link.sh
@@ -13,13 +13,13 @@
 # Otherwise this script is fail-safe, falling back to the original full link
 # command if anything fails.
 
-echo "$LINK " >link.cmd
+echo "$LINK " >link_$PROG.cmd
 exit_value=0
 
 if test "$LINK_AS_NEEDED" = yes; then
   echo "link.sh: \$LINK_AS_NEEDED set to 'yes': invoking linker directly."
-  cat link.cmd
-  if sh link.cmd; then
+  cat link_$PROG.cmd
+  if sh link_$PROG.cmd; then
     exit_value=0
     echo "link.sh: Linked fine"
   else
@@ -49,53 +49,53 @@
 # - Don't remove the last -lm: On HP-UX Vim links OK but crashes when the GTK
 #   GUI is started, because the "floor" symbol could not be resolved.
 #
-  cat link.cmd
-  if sh link.cmd; then
+  cat link_$PROG.cmd
+  if sh link_$PROG.cmd; then
     touch auto/link.sed
-    cp link.cmd linkit.sh
+    cp link_$PROG.cmd linkit_$PROG.sh
     for libname in SM ICE nsl dnet dnet_stub inet socket dir elf iconv Xt Xmu Xp Xpm X11 Xdmcp x w perl dl pthread thread readline m crypt attr; do
       cont=yes
       while test -n "$cont"; do
-        if grep "l$libname " linkit.sh >/dev/null; then
-          if test ! -f link1.sed; then
+        if grep "l$libname " linkit_$PROG.sh >/dev/null; then
+          if test ! -f link1_$PROG.sed; then
             echo "link.sh: OK, linking works, let's try omitting a few libraries."
             echo "link.sh: See auto/link.log for details."
             rm -f auto/link.log
           fi
-          echo "s/-l$libname  *//" >link1.sed
-          sed -f auto/link.sed <link.cmd >linkit2.sh
-          sed -f link1.sed <linkit2.sh >linkit.sh
+          echo "s/-l$libname  *//" >link1_$PROG.sed
+          sed -f auto/link.sed <link_$PROG.cmd >linkit2_$PROG.sh
+          sed -f link1_$PROG.sed <linkit2_$PROG.sh >linkit_$PROG.sh
           # keep the last -lm
-          if test $libname != "m" || grep "lm " linkit.sh >/dev/null; then
+          if test $libname != "m" || grep "lm " linkit_$PROG.sh >/dev/null; then
             echo "link.sh: Trying to omit the $libname library..."
-            cat linkit.sh >>auto/link.log
+            cat linkit_$PROG.sh >>auto/link.log
             # Redirect this link output, it may contain error messages which
             # should be ignored.
-            if sh linkit.sh >>auto/link.log 2>&1; then
+            if sh linkit_$PROG.sh >>auto/link.log 2>&1; then
               echo "link.sh: Vim doesn't need the $libname library!"
-              cat link1.sed >>auto/link.sed
+              cat link1_$PROG.sed >>auto/link.sed
               rm -f auto/pathdef.c
             else
               echo "link.sh: Vim DOES need the $libname library."
               cont=
-              cp link.cmd linkit.sh
+              cp link_$PROG.cmd linkit_$PROG.sh
             fi
           else
             cont=
-            cp link.cmd linkit.sh
+            cp link_$PROG.cmd linkit_$PROG.sh
           fi
         else
           cont=
-          cp link.cmd linkit.sh
+          cp link_$PROG.cmd linkit_$PROG.sh
         fi
       done
     done
     if test ! -f auto/pathdef.c; then
       $MAKE objects/pathdef.o
     fi
-    if test ! -f link1.sed; then
+    if test ! -f link1_$PROG.sed; then
       echo "link.sh: Linked fine, no libraries can be omitted"
-      touch link3.sed
+      touch link3_$PROG.sed
     fi
   else
     exit_value=$?
@@ -107,29 +107,29 @@
 #
 if test -s auto/link.sed; then
   echo "link.sh: Using auto/link.sed file to omit a few libraries"
-  sed -f auto/link.sed <link.cmd >linkit.sh
-  cat linkit.sh
-  if sh linkit.sh; then
+  sed -f auto/link.sed <link_$PROG.cmd >linkit_$PROG.sh
+  cat linkit_$PROG.sh
+  if sh linkit_$PROG.sh; then
     exit_value=0
     echo "link.sh: Linked fine with a few libraries omitted"
   else
     exit_value=$?
     echo "link.sh: Linking failed, making auto/link.sed empty and trying again"
-    mv -f auto/link.sed link2.sed
+    mv -f auto/link.sed link2_$PROG.sed
     touch auto/link.sed
     rm -f auto/pathdef.c
     $MAKE objects/pathdef.o
   fi
 fi
-if test -f auto/link.sed -a ! -s auto/link.sed -a ! -f link3.sed; then
+if test -f auto/link.sed -a ! -s auto/link.sed -a ! -f link3_$PROG.sed; then
   echo "link.sh: Using unmodified link command"
-  cat link.cmd
-  if sh link.cmd; then
+  cat link_$PROG.cmd
+  if sh link_$PROG.cmd; then
     exit_value=0
     echo "link.sh: Linked OK"
   else
     exit_value=$?
-    if test -f link2.sed; then
+    if test -f link2_$PROG.sed; then
       echo "link.sh: Linking doesn't work at all, removing auto/link.sed"
       rm -f auto/link.sed
     fi
@@ -141,7 +141,8 @@
 #
 # cleanup
 #
-rm -f link.cmd linkit.sh link1.sed link2.sed link3.sed linkit2.sh
+rm -f link_$PROG.cmd linkit_$PROG.sh link1_$PROG.sed link2_$PROG.sed \
+  link3_$PROG.sed linkit2_$PROG.sh
 
 #
 # return an error code if something went wrong