[Bug]: absl_stacktrace_test fails on powerpc64le-linux-gnu

### Describe the issue

with the 20250815.1 release, this test fails on powerpc64le-linux-gnu:

complete build logs at
https://buildd.debian.org/status/logs.php?pkg=abseil&arch=ppc64el

66: Test command: /build/reproducible-path/abseil-20250814.1/static/bin/absl_decode_rust_punycode_test
66: Working Directory: /build/reproducible-path/abseil-20250814.1/static/absl/debugging
66: Test timeout computed to be: 1500
62: [ OK ] StackTrace.FixupLowStackUsage (11 ms)
62: [ RUN ] StackTrace.CustomUnwinderPerformsFixup
62: [ OK ] StackTrace.CustomUnwinderPerformsFixup (0 ms)
62: [ RUN ] StackTrace.CanonicalFrameAddresses
62: [ OK ] StackTrace.CanonicalFrameAddresses (0 ms)
62: [ RUN ] StackTrace.NestedSignal
62: absl_stacktrace_test: ./absl/debugging/internal/stacktrace_powerpc-inl.inc:117: void** NextStackFrame(void**, const void*) [with bool STRICT_UNWINDING = true; bool IS_WITH_CONTEXT = true]: Assertion `false && "VDSO is present, but doesn't have expected symbol"' failed.
64: [ OK ] DemangleRegression.DeeplyNestedArrayType (2 ms)
64: [ RUN ] DemangleRegression.ShortOutputBuffer
64: [ OK ] DemangleRegression.ShortOutputBuffer (0 ms)
64: [----------] 3 tests from DemangleRegression (3 ms total)
64:
64: [----------] 1 test from DemangleStringTest
64: [ RUN ] DemangleStringTest.SupportsSymbolNameReturnedByTypeId
59/218 Test #62: absl_stacktrace_test ...............................Subprocess aborted***Exception: 0.02 sec
Running main() from gmock_main.cc
[==========] Running 5 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 5 tests from StackTrace
[ RUN ] StackTrace.FixupNoFixupEquivalence
./absl/debugging/stacktrace_test.cc:107: Skipped
Frame pointers are required, but not guaranteed in OSS

[ SKIPPED ] StackTrace.FixupNoFixupEquivalence (0 ms)
[ RUN ] StackTrace.FixupLowStackUsage
[ OK ] StackTrace.FixupLowStackUsage (11 ms)
[ RUN ] StackTrace.CustomUnwinderPerformsFixup
[ OK ] StackTrace.CustomUnwinderPerformsFixup (0 ms)
[ RUN ] StackTrace.CanonicalFrameAddresses
[ OK ] StackTrace.CanonicalFrameAddresses (0 ms)
[ RUN ] StackTrace.NestedSignal
absl_stacktrace_test: ./absl/debugging/internal/stacktrace_powerpc-inl.inc:117: void** NextStackFrame(void**, const void*) [with bool STRICT_UNWINDING = true; bool IS_WITH_CONTEXT = true]: Assertion `false && "VDSO is present, but doesn't have expected symbol"' failed.

### Steps to reproduce the problem

build on Debian unstable

### What version of Abseil are you using?

20250815.1

### What operating system and version are you using?

Debian unstable

### What compiler and version are you using?

GCC 15 from the gcc-15 branch

### What build system are you using?

cmake version 3.31.6

### Additional context

_No response_