add support for copying arbitrary files

this adds file_copies.prf, which understands the variable COPIES, which
works analogously to INSTALLS.

i've been holding this off for a long time, as it is not without
caveats. however, similar hacks are proliferating all over the code
base, so it's time we formalized it.

in fact, it's the easiest way to fix some nasty shadow build problems,
which is why i'm adding this on the stable branch.

Task-number: QTBUG-52256
Change-Id: Icbe3b9fbb79c952546aad2d467a438d3a69d749f
Reviewed-by: Liang Qi <liang.qi@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

mkspecs/features/file_copies.prf

@@ -0,0 +1,41 @@
+isEmpty(COPIES): return()
+contains(TEMPLATE, .*subdirs): error("COPIES does not work with TEMPLATE=subdirs")
+
+build_pass:build_all: \
+  debug_and_release:debug {
+    # Avoid that multiple build passes race with each other.
+    # This will fail to copy anything if the user explicitly invokes
+    # only the non-primary build. This is unfixable, as at qmake time
+    # we cannot possibly know how make will be invoked, yet we must
+    # predict it here.
+    return()
+}
+
+defineReplace(qtStripProPwd) {
+    return($$relative_path($$1, $$_PRO_FILE_PWD_))
+}
+
+for (cp, COPIES) {
+    isEmpty($${cp}.files): next()
+    pfx = copy_$${cp}
+    for (f, $${cp}.files): \
+        $${pfx}.files += $$absolute_path($$f, $$_PRO_FILE_PWD_)
+    path = $$eval($${cp}.path)
+    isEmpty(path): error("COPY $cp defines no .path")
+    base = $$eval($${cp}.base)
+    isEmpty(base) {
+        $${pfx}.output = $$path/${QMAKE_FILE_BASE}${QMAKE_FILE_EXT}
+    } else: isEqual(base, $$_PRO_FILE_PWD_) {
+        $${pfx}.output = $$path/${QMAKE_FUNC_FILE_IN_qtStripProPwd}
+    } else {
+        eval(defineReplace(qtStripSrcDir_$$cp) { \
+            return(\$\$relative_path(\$\$1, $$val_escape(base))) \
+        })
+        $${pfx}.output = $$path/${QMAKE_FUNC_FILE_IN_qtStripSrcDir_$$cp}
+    }
+    $${pfx}.input = $${pfx}.files
+    $${pfx}.commands = $$QMAKE_COPY ${QMAKE_FILE_IN} ${QMAKE_FILE_OUT}
+    $${pfx}.name = COPY ${QMAKE_FILE_IN}
+    $${pfx}.CONFIG = no_link no_clean target_predeps
+    QMAKE_EXTRA_COMPILERS += $${pfx}
+}

mkspecs/features/spec_pre.prf

@@ -51,5 +51,5 @@ equals(QMAKE_HOST.os, Windows) {
     QMAKE_SH            = sh
 }
 
-CONFIG = qt warn_on release link_prl
+CONFIG = file_copies qt warn_on release link_prl
 QT = core gui