Fix building shared libraries on macOS with --enable-libtorch

[Luthaf]

Description

The configure code was unconditionally adding -Wl;--no-as-needed to the flags, even though these are not valid on macOS.

I'm not sure why this needs --no-as-needed on linux on the first place, @luigibonati do you remember why this is the case?

Type of contribution

• changes to code or doc authored by PLUMED developers, or additions of code in the core or within the default modules
• changes to a module not authored by you
• new module contribution or edit of a module authored by you

Copyright

• I agree to transfer the copyright of the code I have written to the PLUMED developers or to the author of the code I am modifying.

• the module I added or modified contains a COPYRIGHT file with the correct license information. Code should be released under an open source license. I also used the command cd src && ./header.sh mymodulename in order to make sure the headers of the module are correct.

Tests

• I added a new regtest or modified an existing regtest to validate my changes.
• I verified that all regtests are passed successfully on GitHub Actions.

[Luthaf]

The CI errors looks very strange: they seem to be about different whitespaces in parsing output:

#11 663.2 /home/plumed/plumed2/regtest/contour/rt-parse-only/tmp
#11 663.2 Checking for contour
#11 663.5 FAILURE
#11 663.5 Diff for shortcuts.json:
#11 663.5 16c16
#11 663.5 <       "expansion" : "fcc_grp: GROUP ATOMS=1-5184 \nfcc_mat: CONTACT_MATRIX GROUP=1-5184 SWITCH={CUBIC D_0=1.2 D_MAX=1.5} COMPONENTS \nfcc_vfunc: FCCUBIC_FUNC ARG=fcc_mat.x,fcc_mat.y,fcc_mat.z ALPHA=27\nfcc_wvfunc: CUSTOM ARG=fcc_vfunc,fcc_mat.w FUNC=x*y PERIODIC=NO\nfcc_ones: ONES SIZE=5184\nfcc: MATRIX_VECTOR_PRODUCT ARG=fcc_wvfunc,fcc_ones\nfcc_denom: MATRIX_VECTOR_PRODUCT ARG=fcc_mat.w,fcc_ones\nfcc_n: CUSTOM ARG=fcc,fcc_denom FUNC=x/y PERIODIC=NO"
#11 663.5 ---
#11 663.5 >       "expansion" : "fcc_grp: GROUP ATOMS=1-5184\nfcc_mat: CONTACT_MATRIX GROUP=1-5184 SWITCH={CUBIC D_0=1.2 D_MAX=1.5} COMPONENTS\nfcc_vfunc: FCCUBIC_FUNC ARG=fcc_mat.x,fcc_mat.y,fcc_mat.z ALPHA=27\nfcc_wvfunc: CUSTOM ARG=fcc_vfunc,fcc_mat.w FUNC=x*y PERIODIC=NO\nfcc_ones: ONES SIZE=5184\nfcc: MATRIX_VECTOR_PRODUCT ARG=fcc_wvfunc,fcc_ones\nfcc_denom: MATRIX_VECTOR_PRODUCT ARG=fcc_mat.w,fcc_ones\nfcc_n: CUSTOM ARG=fcc,fcc_denom FUNC=x/y PERIODIC=NO"

which I don't see how these changes could have introduced??

[GiovanniBussi]

@gtribello do you know the origin of this failure? It seems related to the parser

[carlocamilloni]

@Luthaf can you retarget to v2.10 please?

[Luthaf]

Sure, I'll rebase as well to remove the extra commits.

I'll need this and a couple of other things for my work, should I also backport #1122 to v2.10?

[carlocamilloni]

yes for the moment everything that can be considered bug fixing should target v2.10 or v2.9

[GiovanniBussi]

Regarding #1122, I just backported it to v2.10