RFR: JDK-8313790: [arm32] Specify -marm when building without an ABI profile

[Erik Joelsson]

On Fri, 4 Aug 2023 16:17:04 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> See [JDK-8288719](https://bugs.openjdk.org/browse/JDK-8288719) and subsequent [discussion](https://mail.openjdk.org/pipermail/build-dev/2022-May/034635.html) back in 2022.
> 
> On Arm, we can generate either arm- or thumb-code (`-marm` or `-mthumb`). 
> 
> At the moment, if we don't specify an ABI profile (`--with_abi_profile`) when configuring the build, we call gcc without `-marm` or `-mthumb`. Then we use whatever the toolchain defaults too, which is pretty much random (it depends on how the toolchain itself had been built). That can cause really rare but tricky problems when combining static assembly and C++ code (See e.g. JDK-8288719).
> 
> I propose to always specify `-marm` as default, unless an ABI profile is given, to prevent such errors.
> 
> Thanks to @marchof for testing this.

Marked as reviewed by erikj (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/15162#pullrequestreview-1704801394