The list of features a Wasm object/binary file can emit can differ
from the list of cpu features. The reason for this is because the
"target_features" section also contains linker features. An example
of this is the "shared-mem" feature, which is a feature for the linker
and not that of the cpu target as defined by LLVM.
Adds a test for inferring features based on a different object file.
Also provides a test case where cpu features are explicitly set on
a library where the end result will output said target features.
When an object file or binary contains the target_features section
we can now parse and then dump its contents in string format so
we can use them in our linker tests to verify the features section.
When the result is not being stripped, we emit the `target_features`
section based on all the used features. This includes features
inferred from linked object files.
Considering we know all possible features upfront, we can use an
array and therefore do not have to dynamically allocate memory.
Using this trick we can also easily order all features based
the same ordering as found in `std.Target.wasm` which is the same
ordering used by LLVM and the like.
Verifies disallowed and used/required features. After verifying,
all errors will be emit to notify the user about incompatible
features. When the user did not define any featureset, we infer
the features from the linked objects instead.
These ifs were missing a case for f80 which should have shifted by one,
but we can just compute the correct value instead. Also, we want the
fractional bits to be a multiple of four, not the mantissa bits, since
the mantissa could have a leading one which we want to be separated.
Global constant initializers can reference functions, so forward declare
the constants and initialize them later with the function definitions,
which guarantees that they appear after all declarations.
