Makefiles: Normalize compiler-generated depfile paths

Even though Makefile generators pass source files and include directories by absolute path to the compiler, the compiler may generate depfile paths relative to the current working directory. For example, ccache with CCACHE_BASEDIR may transform paths this way. When reading a depfile, convert relative dependencies to absolute paths before placing them in compiler_depend.make, which is later evaluated in the top-level build directory.

Fixes: #22364 (closed)
Backport: release:HEAD^2
Topic-rename: makefile-normalize-depfile

changed milestone to %3.21.0

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@jrosdahl can you, if possible, test this fix?

@brad.king Maybe this fix must be also propagated to 3.20.* version because the problem was introduced in 3.20.0.

changed title from compiler dependencies: ensure ccache full support to Makefiles: Normalize compiler-generated depfile paths

added gen:makefiles label

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• 6a6efdca - Makefiles: Normalize compiler-generated depfile paths

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assigned to @brad.king

added 1356 commits

• 6a6efdca...6372e74e - 1355 commits from branch cmake:master
• 6bc6ffb9 - Merge branch 'backport-3.20-makefile-normalize-depfile'

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added 149 commits

• 6bc6ffb9...4f69bf09 - 148 commits from branch cmake:master
• 30926620 - Merge branch 'backport-3.21-makefile-normalize-depfile'

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Do: stage

added workflow:nightly-testing label and removed workflow:in-review label

@jrosdahl can you, if possible, test this fix?

Works fine for me.

Do: merge

merged

mentioned in commit 7fdd8066

mentioned in commit 0cd8bba0

removed workflow:nightly-testing label

mentioned in commit 77abc295

resolved all threads

changed milestone to %3.20.6