Index: Makefile.in
==================================================================
--- Makefile.in
+++ Makefile.in
@@ -1598,11 +1598,11 @@
 
 # Install the SQLite TCL extension in a way that is appropriate for $TCLSH_CMD
 # to find it.
 #
 tclextension-install:	tclsqlite3.c
-	$(TCLSH_CMD) $(TOP)/tool/buildtclext.tcl --cc "$(CC)" $(CFLAGS) $(OPT_FEATURE_FLAGS) $(OPTS)
+	$(TCLSH_CMD) $(TOP)/tool/buildtclext.tcl --destdir "$(DESTDIR)" --cc "$(CC)" $(CFLAGS) $(OPT_FEATURE_FLAGS) $(OPTS)
 
 # Install the SQLite TCL extension that is used by $TCLSH_CMD
 #
 tclextension-uninstall: 
 	$(TCLSH_CMD) $(TOP)/tool/buildtclext.tcl --uninstall

Index: tool/buildtclext.tcl
==================================================================
--- tool/buildtclext.tcl
+++ tool/buildtclext.tcl
@@ -15,6 +15,7 @@
    --info               Show info on existing SQLite TCL extension installs
    --install-only       Install an extension previously build
    --uninstall          Uninstall the extension
+   --destdir DIR        Installation root (used by "make install DESTDIR=...")
 
 Other options are retained and passed through into the compiler.}
 
@@ -25,6 +26,7 @@
 set infoonly 0
 set CC {}
 set OPTS {}
+set DESTDIR ""; # --destdir "$(DESTDIR)"
 for {set ii 0} {$ii<[llength $argv]} {incr ii} {
   set a0 [lindex $argv $ii]
   if {$a0=="--install-only"} {
@@ -42,6 +44,9 @@
   } elseif {$a0=="--cc" && $ii+1<[llength $argv]} {
     incr ii
     set CC [lindex $argv $ii]
+  } elseif {$a0=="--destdir" && $ii+1<[llength $argv]} {
+    incr ii
+    set DESTDIR [lindex $argv $ii]
   } elseif {[string match -* $a0]} {
     append OPTS " $a0"
   } else {
@@ -245,7 +250,7 @@
 
 if {$install} {
   # Install the extension
-  set DEST2 $DEST/sqlite$VERSION
+  set DEST2 ${DESTDIR}$DEST/sqlite$VERSION
   file mkdir $DEST2
   puts "installing $DEST2/pkgIndex.tcl"
   file copy -force pkgIndex.tcl $DEST2
Index: tool/buildtclext.tcl
==================================================================
--- tool/buildtclext.tcl
+++ tool/buildtclext.tcl
@@ -196,11 +196,19 @@
   # Figure out where the extension will be installed.  Put the extension
   # in the first writable directory on $auto_path.
   #
   set DEST {}
   foreach dir $auto_path {
-    if {[file writable $dir]} {
+    if {[string match //*:* $dir]} {
+      # We can't install to //zipfs: paths
+      continue
+    } elseif {"" ne $DESTDIR && ![file writable $DESTDIR]} {
+      continue
+    }
+    set dir ${DESTDIR}$dir
+    if {[file writable $dir] || "" ne $DESTDIR} {
+      # the dir will be created later ^^^^^^^^
       set DEST $dir
       break
     } elseif {[glob -nocomplain $dir/sqlite3*/pkgIndex.tcl]!=""} {
       set conflict [lindex [glob $dir/sqlite3*/pkgIndex.tcl] 0]
       puts "Unable to install. There is already a conflicting version"
@@ -214,11 +222,11 @@
     puts "None of the directories on \$auto_path are writable by this process,"
     puts "so the installation cannot take place.  Consider running using sudo"
     puts "to work around this problem.\n"
     puts "These are the (unwritable) \$auto_path directories:\n"
     foreach dir $auto_path {
-      puts "  *  $dir"
+      puts "  *  ${DESTDIR}$dir"
     }
     exit 1
   }
 }
 
@@ -248,12 +256,12 @@
 }
 
 
 if {$install} {
   # Install the extension
-  set DEST2 ${DESTDIR}$DEST/sqlite$VERSION
+  set DEST2 $DEST/sqlite$VERSION
   file mkdir $DEST2
   puts "installing $DEST2/pkgIndex.tcl"
   file copy -force pkgIndex.tcl $DEST2
   puts "installing $DEST2/$OUT"
   file copy -force $OUT $DEST2
 }