Handle macOS cross-compilation for Rust extensions

[mlafeldt]

Fixes #158
Fixes duckdb/extension-template-rs#28

Testing on my ARM Mac:

❯ make
...
Creating extension binary:
 - Input file: ./build/debug/librusty_quack.dylib
 - Output file: ./build/debug/rusty_quack.duckdb_extension
 - Metadata:
   - FIELD8 (unused)            = EMPTY
   - FIELD7 (unused)            = EMPTY
   - FIELD6 (unused)            = EMPTY
   - FIELD5 (abi_type)          = C_STRUCT_UNSTABLE
   - FIELD4 (extension_version) = 26f23da
   - FIELD3 (duckdb_version)    = v1.3.2
   - FIELD2 (duckdb_platform)   = osx_arm64
   - FIELD1 (header signature)  = 4 (special value to identify a duckdb extension)
./configure/venv/bin/python3 -c "import shutil;shutil.copyfile('./build/debug/rusty_quack.duckdb_extension', './build/debug/extension/rusty_quack/rusty_quack.duckdb_extension')"

❯ file ./build/debug/extension/rusty_quack/rusty_quack.duckdb_extension
./build/debug/extension/rusty_quack/rusty_quack.duckdb_extension: Mach-O 64-bit dynamically linked shared library arm64

❯ make DUCKDB_PLATFORM=osx_arm64
...
Creating extension binary:
 - Input file: ./build/debug/librusty_quack.dylib
 - Output file: ./build/debug/rusty_quack.duckdb_extension
 - Metadata:
   - FIELD8 (unused)            = EMPTY
   - FIELD7 (unused)            = EMPTY
   - FIELD6 (unused)            = EMPTY
   - FIELD5 (abi_type)          = C_STRUCT_UNSTABLE
   - FIELD4 (extension_version) = 26f23da
   - FIELD3 (duckdb_version)    = v1.3.2
   - FIELD2 (duckdb_platform)   = osx_arm64
   - FIELD1 (header signature)  = 4 (special value to identify a duckdb extension)
./configure/venv/bin/python3 -c "import shutil;shutil.copyfile('./build/debug/rusty_quack.duckdb_extension', './build/debug/extension/rusty_quack/rusty_quack.duckdb_extension')"

❯ file ./build/debug/extension/rusty_quack/rusty_quack.duckdb_extension
./build/debug/extension/rusty_quack/rusty_quack.duckdb_extension: Mach-O 64-bit dynamically linked shared library arm64

❯ make DUCKDB_PLATFORM=osx_amd64
...
Creating extension binary:
 - Input file: ./build/debug/librusty_quack.dylib
 - Output file: ./build/debug/rusty_quack.duckdb_extension
 - Metadata:
   - FIELD8 (unused)            = EMPTY
   - FIELD7 (unused)            = EMPTY
   - FIELD6 (unused)            = EMPTY
   - FIELD5 (abi_type)          = C_STRUCT_UNSTABLE
   - FIELD4 (extension_version) = 26f23da
   - FIELD3 (duckdb_version)    = v1.3.2
   - FIELD2 (duckdb_platform)   = osx_amd64
   - FIELD1 (header signature)  = 4 (special value to identify a duckdb extension)
./configure/venv/bin/python3 -c "import shutil;shutil.copyfile('./build/debug/rusty_quack.duckdb_extension', './build/debug/extension/rusty_quack/rusty_quack.duckdb_extension')"

❯ file ./build/debug/extension/rusty_quack/rusty_quack.duckdb_extension
./build/debug/extension/rusty_quack/rusty_quack.duckdb_extension: Mach-O 64-bit dynamically linked shared library x86_64

[samansmink]

Looks good, thanks @mlafeldt!

[JAicewizard]

Does not fix #158

[mlafeldt]

We also need to update the Rust template to actually incorporate the fix. See duckdb/extension-template-rs#29

[mlafeldt]

And I think we also have to update https://github.com/duckdb/community-extensions/blob/main/extensions/rusty_quack/description.yml#L15 so rusty_quack gets redeployed.

[carlopi]

You are also welcome to send a PR bumping rusty_quack descriptor (and adding yourself as maintainer) after duckdb/extension-template-rs#29 is in. Thanks!!

[mlafeldt]

@carlopi Did both in duckdb/community-extensions#538