This improves the portability of the linker script and allows lld to link rom.o

Dot assignment inside an output section has an inconsistent behavior
which makes lld difficult to implement.
See https://bugs.llvm.org/show_bug.cgi?id=43083

Dropping `. =` turns out to be beneficial to older GNU ld as well
because we can delete an ld check detecting "cannot move location
counter backwards".

--
Changes v2 -> v3
* Add `first` to avoid overloading `location`
* Delete startsym from the parameters

Signed-off-by: Fangrui Song <mask...@google.com>
---
 scripts/layoutrom.py | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/scripts/layoutrom.py b/scripts/layoutrom.py
index caed387..caa182a 100755
--- a/scripts/layoutrom.py
+++ b/scripts/layoutrom.py
@@ -331,19 +331,25 @@ def outSections(sections, useseg=0):
     return out
 
 # Write LD script includes for the given sections using relative offsets
-def outRelSections(sections, startsym, useseg=0):
+def outRelSections(sections, useseg=0):
     sections = [(section.finalloc, section) for section in sections
                 if section.finalloc is not None]
     sections.sort(key=operator.itemgetter(0))
     out = ""
+    first = True
     for addr, section in sections:
         loc = section.finalloc
         if useseg:
             loc = section.finalsegloc
-        out += ". = ( 0x%x - %s ) ;\n" % (loc, startsym)
+        if first:
+            out += ". += 0x%x - _reloc_init_end ;\n" % (loc,)
+            first = False
+        elif location != loc:
+            out += ". += 0x%x ;\n" % (loc-location,)
         if section.name in ('.rodata.str1.1', '.rodata'):
             out += "_rodata%s = . ;\n" % (section.fileid,)
         out += "*%s.*(%s)\n" % (section.fileid, section.name)
+        location = loc + section.size
     return out
 
 # Build linker script output for a list of relocations.
@@ -444,7 +450,7 @@ def writeLinkerScripts(li, out16, out32seg, out32flat):
        sec32all_start,
        multiboot_header,
        relocstr,
-       outRelSections(li.sections, 'code32flat_start'))
+       outRelSections(li.sections))
     out = COMMONHEADER + out + COMMONTRAILER + """
 ENTRY(%s)
 PHDRS
-- 
2.26.0.292.g33ef6b2f38-goog
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